Most collectors know of the Cripple Creek district from seeing souvenir-type specimens of roasted gold telluride ore. When telluride ore samples are heated above a few hundred degrees Celsius, the tellurium vaporizes, leaving bubble-like blobs of gold behind. However, fine specimens of melonite, calaverite, sylvanite, krennerite, amethyst, and turquoise from Cripple Creek can be seen in many museums and are occasionally available to collectors. In 2003, excellent specimens of creedite, some with gearksutite, celestine, and/or botryoidal rhodochrosite, were released from a 2001 discovery (Moore, 2004). However, considering the detrimental effects that current large-volume surface mining methods, stringent reclamation requirements, limited access, and limited reserves have on specimen recovery, the Cripple Creek area is unlikely to produce significant new finds for more than the next decade or so.
The senior author's interest in the district dates from the early 1970's, when he directed an annual geology field course headquartered in Florissant, about 20 miles north of Cripple Creek. Included in the course was a short field trip to examine the major rock types of the district; we also visited the Molly Kathleen mine (still operating today), where, each year, a dozen or so college students, their professor, and a tour guide were squeezed into a man cage that was not much larger than a phone booth.
The junior author actively mapped and explored the area from the late 1980's through the early 1990's. Ultimately he was unable to acquire the ground he wanted, and moved on. However, both authors today remain interested in the district and its minerals, and fascinated by the history of Cripple Creek, one of the most colorful of Colorado's mining camps.
LOCATION AND ACCESS
The town of Cripple Creek, in Teller County, lies 23 miles west of Colorado Springs and 10 miles southwest of Pikes Peak. The Cripple Creek gold mining district lies to the east of Cripple Creek town and to the north of the town of Victor. Covering only a few square km, it is the third most productive gold district in the United States (after the Homestake mine in Lead, South Dakota and the Carlin district in Nevada). Cripple Creek's roughly 500 mines have produced more than 22 million troy ounces (614 metric tons) of gold and an unknown quantity of silver since production began in 1891. This is about half of Colorado's total gold output of 44 million ounces since 1860 (Davis and Streufert, 1990) and about 5% of total U.S. production between 1900 and 2000. Except for a period from the 1960's through the 1980's, significant production has been nearly continuous since the commencement of mining in 1891.
A large open pit operation at Cripple Creek was opened in 1995, and since then it has produced approximately 12 million tons of ore yielding 250,000 to 300,000 ounces of gold per year. The ore is quite low-grade-on the order of 0.03 troy ounces of gold per ton (quite a contrast from the 1 to 2 ounces per ton from ore mined in the early 1900's!) Projections indicate that this mega-pit will produce an additional 3.5 million ounces of gold. Mining is permitted through 2012, with final reclamation scheduled for 2021 (AngloGold, 2001). However, additional known resources of approximately 1.4 million ounces (Pontius, 1996) may allow mining to continue beyond 2012.
The modern mine is a "standard" heap-leach facility. The ore is mined and crushed to small gravel size, then sent by conveyor or truck to leach pads where a dilute sodium cyanide solution is sprayed on the pile. The cyanide dissolves the gold; the solution is then collected from the base of the pile and is run through a precipitation plant, where gold is recovered by carbon adsorption. An electrowinning process follows, and the final product is cast into dor "buttons" containing about 75 percent gold and 25 percent silver. With an initial capital investment of some $150 million, the mine currently employs about 300 people (AngloGold, 2001).
About 90% of the Cripple Creek district (more than 4,800 patented mining claims) is now controlled by the Cripple Creek & Victor Gold Mining Company, a 33:67 joint venture between AngloGold North America and the Golden Cycle Corp. (Cripple Creek & Victor Gold Mining Co., 1999). This property is clearly posted, and trespassing is both prohibited and dangerous. However, CC&V staff offer tours for organized groups, and casual visitors can enjoy a well maintained trail system in the Vindicator Valley, just north of Victor. The trail provides access to many clearly identified, standing historic mine structures and ruins. The Golden Loop Historic Parkway, which offers a spectacular overlook at the American Eagle mine site, can be enjoyed by car. A few trails are marked, but visitors otherwise are strongly discouraged from exploring the district on foot without permission.
The Pikes Peak gold rush of 1859 largely bypassed the Pikes Peak region. The mountain was used as a landmark by westward-moving gold seekers, but the real rush was to the north, at Idaho Springs and Central City. The Pikes Peak area offered only unpromising red granite and gray volcanic rocks, and the local streams rewarded even the most persistent sourdoughs with little more than a show. Most prospectors who visited the area did not stay long, but instead continued their quest farther west and north.
Among those drawn west by the rush were Sam Womack and his son Bob, a 17-year-old eager to learn about mining. The Womacks came west from Kentucky in 1861, just as the Civil War was heating up. Soon the rest of the family followed them to the Clear Creek/Georgetown area, where Sam, Bob, and Bob's brother William busied themselves with gold and silver mining, milling and production. Although some later acquaintances thought of Bob as a drunken cowboy with little or no knowledge of mining, his experience in the 1860's made him a much more savvy prospector than most of the people who became involved in seeking valuable metals.
By 1867, Sam Womack had accumulated substantial wealth, but apparently at the cost of his health. Thinking that mining was bad for him, he moved his family to the Sunview Ranch in the Colorado City area, 3 miles west of Colorado Springs. There they took up cattle ranching on 640 acres along Little Fountain Creek. Bob became an expert rider and explored widely, hunting game and panning the streams. He had been bitten by the gold bug, and for most of the rest of his life he took far more interest in prospecting than in ranching or other occupations.
In 1871, friends of the Womacks named Welty decided to leave their ranch north of Colorado Springs and settle in the Pikes Peak country to the southwest. They built their squatters' cabin in Pisgah Park, southwest of Pikes Peak, near a spring that supplied a nearby creek. One story often told is that the Weltys needed to build a spring house to protect the spring from wild animals; while they were building it, somebody lost control of a log, a gun was accidentally discharged, and a "pet" calf, startled by the shot, jumped the stream, stumbled, and broke its leg (Sprague, 1953). Levi Welty supposedly said something like "Well, boys, this sure is some cripple creek," and the name stuck.
The Womacks continued to operate the Sunview Ranch on Little Fountain Creek through the middle 1870's. In 1873, Bob bumped into members of Ferdinand Hayden's Geographical and Geological Survey of the Territories, who were eating lunch in the nearby town of Fountain. Among those in the party was Theodore Lowe, a cousin of Bob's brother-in-law. Made curious, perhaps, by Bob's stories, the exploring party visited the Cripple Creek area, where they noted a gold show in volcanic rocks and then moved on. In 1874, a member of the group, H. T. Wood, returned with some enthusiasts from Fountain and dug a 100-foot prospect hole in the middle of what later became the richest part of the Cripple Creek district (Sprague, 1953). They found what was described as "white iron," meaning arsenopyrite; it was instead probably one of the gold-silver tellurides, but they thought it was worthless and left.
By 1875 the Womacks had realized that, as the population of the Colorado City/Colorado Springs area was booming, it would be useful to own summer grazing land in the mountains. In 1876 they bought the Weltys' squatters' rights in Pisgah Park, and Bob homesteaded an additional 160 acres 2 miles to the south, in Arequa Gulch. His brother William, with his new wife, moved into the Welty cabin, while Bob built a shack nearby, in a place he dubbed "Poverty Gulch."
Some writers, notably Cripple Creek historian Leland Feitz, think the name Cripple Creek came up Ute Pass with the Womacks. Although they came from Kentucky, the Womacks had roots near a place still called Cripple Creek, Virginia (MacKell, 2003), and they may have named the creek in memory of their roots. Like many stories that aren't very colorful, this one may be closer to the truth than others (such as the one involving the Weltys' pet calf, above).
In May of 1878, Bob Womack picked up a piece of volcanic "float" in Poverty Gulch. Theodore Lowe talked a Denver assayer into analyzing it, and it turned out to be gold ore worth $200 per ton (nearly 10 troy ounces of gold per ton-good enough to cause a stampede in most places!). Bob recognized that the surficially altered sample, which he had found in the gravel scree, could have come from nearly anywhere upslope. He followed the "float trail" uphill for 2 miles, buoyed by the results of occasional assays. On periodic binges in Colorado City, Bob bragged about the gold deposit he was tracing up Poverty Gulch, but many viewed him as a crackpot, and only one man, Henry Cocking, took the trouble to visit the site and stake a claim. In 1881, Cocking drove an entry into the hillside at the highest point of Bob's float trail, stopping just short of a $3,000,000 vein.
In 1884, two men dug a prospect hole on the east side of a barren volcanic peak called McIntyre Mountain, 13 miles west of the Womack homesteads. After erecting a sign naming the hole the Teller Placer, the two left for Canon City. Soon the claimants announced a $2,000-per-ton assay of material from the claim, and within a short time thousands of people were camped out on the slopes around Mclntyre. Bob Womack, thinking Mclntyre Mountain was a strange place for a placer, talked with local old-timers and confirmed his suspicion that the story was a hoax, possibly cooked up by Canon City merchants to drum up business (Sprague, 1953). Unfortunately, when word reached Colorado Springs, the press confused McIntyre Mountain with another volcanic peak, Mt. Pisgah, which happens to lie just west of Poverty Gulch and the future Cripple Creek town site. For most people, the incorrect news stories discrediting Mt. Pisgah dealt a fatal blow to any enthusiasm Bob Womack's stories about Cripple Creek gold might have generated.
The Womacks sold both of their Cripple Creek-area homesteads in 1885. Eventually they were bought by Horace Bennett and Julius Myers, who formed the Houseman Cattle and Land Company. Bob Womack stayed in the area, doing odd jobs for Bennett and Myers and continuing to follow his float trail. In 1886, he staked a claim (the Grand View) where the float trail appeared to end. After selling a two-thirds interest to Edwin Wallace in 1887, Bob talked a dentist friend, Dr. John Grannis, into grubstaking him for a half interest in 1889. (Notice that the shares of mining claims sometimes add up to some figure other than 100%!) Wallace abandoned the claim, and in 1890 Bob re-occupied, re-staked, and re-named the claim, calling it the El Paso. Dr. Grannis hired Colorado College professor Henry Lamb to check out the claim, and Professor Lamb's assays were encouraging; they suggested the presence of ore worth up to $250 per ton. However, the source of the gold wasn't clear.
Incredibly, Bob and Dr. Grannis still couldn't find anyone to take the area seriously. In frustration, they placed samples of their ore in a Colorado Springs store window, thinking someone might take an interest. The someone who did was Ed De La Vergne, an unemployed Colorado Springs resident whose brother owned a furniture store across the street. By this point in 1890, Ed had just finished taking Professor Lamb's assaying course. He suspected that the ore samples in the store window were sylvanite, a gold-silver telluride first described in Romania but relatively unknown to American assayers. Ed tracked down the samples' owners, and, a few days later, met with Bob Womack, Dr. Grannis, Professor Lamb and Fred Frisbee, a friend of Ed's. After Bob described the results of his 12-year search, Ed, keeping his suspicions secret, checked the area out for himself in January, 1891. He and Fred Frisbee wandered around for an adventurous month, supposedly eating pack rats, getting sick on snow water, and being bitten by a raven. They also collected samples and, while staying at the Broken Box ranch in Poverty Gulch, Ed put an ore sample on a hot stove. Golden bubbles appeared on the surface, confirming Ed's suspicions.
Ed De La Vergne's interest in the area suggested to others in Colorado Springs that maybe Bob Womack wasn't crazy after all. However, one last, untimely hindrance to a gold rush appeared in a news article in February, 1891. The story reported a find of something that had been misidentified as gold, saying that the find had occurred at Florissant, not far from Mt. Pisgah (actually the distance between them is about 15 miles). The story temporarily deflated interest in the Cripple Creek area for some, but Ed had already staked two claims adjacent to Bob's El Paso lode. Bob soon heard that others had staked claims, and that they planned to meet at Cripple Creek in April to form a mining district. The organizers focused on an area about 6 miles square (23,000 acres) that included most of the volcanic rocks of the Cripple Creek basin. By September, people were flooding into the district, staking hundreds of claims in the Poverty Gulch area and in the country immediately to the south.
Despite all of the interest, not much money followed the immigrants in the first rush to Cripple Creek. Few of the early prospectors had the resources needed to turn a prospect into a mine. However, in August. 1891. Count James Pourtales, owner of the Broadmoor Dairy and several other properties in Colorado Springs, met Ed De La Vergne. Ed had the prescience to predict that the district would create many millionaires. Pourtales decided he needed to check the area out for himself, and in mid-August he and a friend, an experienced prospector, visited the district. In November, Pourtales announced that he had bought a claim for $80,000. In a very short time, dozens of other potential investors sent agents to look into the district, and by 1892 hundreds of claims had changed hands. Stock sales and prices skyrocketed. Unfortunately for Bob Womack, he had sold his remaining half interest in the El Paso lode to Dr. Grannis for $300. The doctor then sold 80 percent of it for $8000, and shortly thereafter a judge paid $10,000 for a ten-percent interest (Sprague, 1953). In 1892, the sheriff of Colorado Springs supposedly claimed that the town had seen a precipitous drop in crime because the criminals had all moved to Cripple Creek.
Gold mining wasn't the only way to make a killing in Cripple Creek. Several Colorado Springs investors staked 140 acres of geologically unpromising land around the north and east sides of Bennett and Myers' Broken Box Ranch, naming the site Hayden Placer. Before they even had a patent, they began subdividing the site and selling lots. By February, 1892, the Hayden Placer town site was broken into 1320 lots (Sprague, 1953). Recognizing the danger of losing a golden opportunity. Bennett and Myers platted the hilliest part of the Broken Box Ranch, naming their new town site "Fremont." Its 30 blocks and 766 lots showed no regard for topography, as can still be observed by flatlanders who gasp their way up and down the hilly streets of what was once Fremont (now a part of modern-day Cripple Creek).
The founders of Hayden Placer, which was already popularly called Cripple Creek, barred most of the businesses most typically in demand in a raw mining town. Saloons, dance halls and bordellos were forbidden, and so were forced to locate in Fremont. With 1000 new residents arriving each month, the demand for lots soon consumed Hayden Placer, Fremont, the rest of the Broken Box Ranch, and much of the surrounding country. Finally, in February of 1893, residents of the two communities voted to combine the towns and formally name the new metropolis "Cripple Creek."
As is often the case, some of the richest mines in the district were discovered and developed in unlikely ways. For example, the deposit exploited by the Gold Coin mine, located in the heart of downtown Victor, was accidentally discovered when the property was excavated for the foundation of a new hotel. The deposit worked by the Pharmacist mine was supposedly discovered by a druggist who threw his hat into the air near the (now) ghost town of Altman and started digging where it landed. He is said to have become one of the district's 30 millionaires (Lewis, 1982).
Especially unlikely is the story of how the Portland mine, the district's biggest producer, came into being. Several characters were involved in the saga. Winfield Scott Stratton, a Colorado Springs carpenter, was one of the early visitors to Bob Womack's cabin in 1891. Having spent at least 17 unproductive summers prospecting for gold in various parts of Colorado, Stratton recognized the importance of training. He took a course in blowpipe analysis, worked in a gold mill, and studied metallurgy. However, he didn't like most people, and when he visited Cripple Creek in 1891 he picked Battle Mountain, north of the present town of Victor, partly to get away from tenderfeet and partly because the area straddles the boundary between the volcanic rock units and the surrounding granite. Most people had considered that area to be "unpromising," but on August 4, 1891, Stratton filed the Independence and other claims, collecting samples that assayed to $360 per ton.
Jimmie Burns was a true tenderfoot, and it's odd that he and Stratton developed a liking for each other. In January of 1892, Burns and his partner, Jimmie Doyle, discovered that, in the confusion of shifting, relocating claims, a tiny piece of Battle Mountain remained unstaked. The orphan plot, measuring just 0.069 acre, was nestled among surrounding claims, any of which might have the legal rights to minerals occurring there, since, according to the apex law, if the high point of a vein occurs on or under your land, you have the right to follow and exploit it indefinitely along its dip (Bates and Jackson, 1980).
With the help of John Harnan, Burns and Doyle found a rich sylvanite vein, which they eventually named the Portland vein. Recognizing the legal problems that were sure to develop when the surrounding groups learned of the find, Burns, Doyle and Harnan removed ore at night, carrying it to Pueblo to be smelted. In this way they accumulated $70,000 in a year or so. In August of 1893, Burns couldn't keep the secret any longer and confided it to his friend Stratton.
About this time, Stratton was having troubles of his own. By 1893, his Washington and Independence claims seemed to be eating up more money than they produced. In frustration, and despite his dislike for the vultures waiting to buy out the little guys in the district, Stratton sold a 30-day option on his Independence mine to a San Francisco mining syndicate. He could hardly believe it when they agreed to pay his asking price of $155,000 if they liked what they saw during the option period. Just before the 30 days were to begin, Stratton went into an abandoned crosscut to clear out his equipment. There, he discovered a vein that assayed $380 per ton. He covered it up as well as he could and spent the next four weeks biting his nails. Incredibly, the syndicate's crew moved in but missed the vein. A few days before the option was up, they abandoned the effort, and the legal rights to the Independence, which eventually became one of the district's top four producers, reverted to Stratton. By September of 1893, the mine's prospects looked so good that Stratton vowed to cap his income at $2000 per day. Nevertheless, he became the district's first millionaire six months later.
After Burns' revelation about the Portland, Stratton grasped three important facts. First, he recognized that Burns' and Doyle's $70,000 wasn't nearly enough to resolve the legal problems that were about to fall on their heads. Second, he realized that the Portland find probably related to his own Independence discovery, 700 feet away. Finally, he recognized that his own rapidly accumulating wealth might help to keep at least a few of the most important mines out of the hands of the speculators and absentee owners. Stratton therefore proposed an alliance. To finance the coming battle, he increased production from the Independence, and by October of 1893, Burns, Doyle and Harnan had accumulated an additional $50,000 from the Portland.
When the truth about the Portland find came out, 27 people filed suit, asking for a total of $3,000,000. Stratton hired Verner Z. Reed to defend the Portland. Using Stratton's money, Reed bought out some claimants and countersued others, claiming that Stratton's properties contained the apexes of their veins. Reed then brought out his "shock and awe" weapons, arranging for the Portland Gold Mining Company to declare a $90,000 dividend. Its stock soared, and the remaining plaintiffs, recognizing the strength of their adversaries, sold out for $1,025,000, much of which was borrowed by Stratton. The resulting Portland property now covered 183 acres. Reed issued 3 million shares of Portland stock, of which Stratton received 731,000 shares. Over the next 90 years The mine produced a total of more than 3 million ounces of gold, worth over $60,000,000 (Vanderwalker and Levine, 1989). Some of Reed's acquisitions were also joined to the Stratton properties. The Independence ended up covering 112 acres, eventually producing over $27,000,000 in gold. In 1899 Stratton sold it to a British company for $11,000,000.
The district's population rapidly grew from an estimated 500 scattered souls in 1890 to 55,000 by 1900. At the peak of the mining boom there were 15 separate towns scattered over the hillsides. (Only two remain: Cripple Creek at the north end of the district and Victor to the south.) Increasing production through the 1890's allowed the district to shake off disasters that might have proven fatal elsewhere. Two fires in April of 1896 destroyed about a third of Cripple Creek, including many ramshackle buildings in the center of town. But recovery was rapid, and new, more permanent brick and stone structures were built (these survived intact until the arrival of gambling in 1991). Similarly, most of Victor went up in smoke in August, 1899. As at Cripple Creek, the fire was a blessing in disguise, leading to construction of stronger brick structures.
In 1900, the year after Stratton sold the Independence mine, Cripple Creek's gold production peaked at 878,067 ounces (Lovering and Goddard, 1950). Total production through 1900 was 3.4 million ounces. By this time, the district had almost 500 active mines, operated by 8000 miners (Feitz, 1967) earning an average of $3 per day (Lewis, 1982). These wages were often spent in the usual ways associated with miners (e.g. in the notorious red-light district on Meyers Avenue). Cripple Creek alone was estimated to contain 150 saloons. The district was served by three major rail lines (making 56 trips per day) as well as two trolley cars (AngloGold, 2001). Most of the gold ore was shipped to roasting plants in Colorado City, on the west side of Colorado Springs. (More than 12 million tons of tailings still reside there.) Victor's streets were literally paved with gold, as the low-grade dump material from many of the nearby mines was mixed with the gravel road base. This was the era when Lowell Thomas worked at the Victor newspaper. Jack Dempsey mucked ore in the Independence mine, and promoters in Gillette staged the only "legal" bullfight ever permitted in the United States.
By 1900, the deeper mines were having trouble with water, and plans were begun to drill drainage tunnels in several places. The El Paso tunnel, begun in 1903 and completed in 1904, gave a brief respite, but rapidly deepening mines and limited pumping technology had rendered it useless by 1906. Serious flooding crippled the El Paso mine and drove down stock values in 1906, stimulating planning for a new tunnel. The Roosevelt tunnel, begun in 1907, was 800 feet deeper than the El Paso. Eventually 4.6 miles long, the tunnel took 10 years and $815,000 to complete (Sprague, 1953), but it permitted mining in many new parts of some of the best mines and restored some of the confidence that had been lost after production peaked. The Roosevelt tunnel remained effective until the 1930's, at which point work began on the last of the district's drainage tunnels: the Carlton tunnel. Over 6 miles long, it was finished in 1941, and presently drains everything above an elevation of 6900 feet. Ironically, no sooner was the Carlton Tunnel completed than World War II began, with gold mining ceasing shortly thereafter by Presidential decree.
Another blow to confidence in the district came with labor problems that began in 1903. By this time, the Western Federation of Miners union had enrolled over 3,500 men in the Cripple Creek area, the largest contingent in the west. The area was reputed to offer better pay and working conditions than most, but an attempt by mine owners to increase the length of the working day and a power play by W.F.M. officials started a violent, bitter battle between the miners and owners. By the time the dispute ended in 1904, shootings and bombings had killed at least 17 men, and the W.F.M. was on its way out of the district.
Although production from the district declined after 1900, a few mines produced spectacular surprises late in the district's history. The Cresson mine, located in the south-central part of the district, is an example. Begun in 1894 and obtained by J. R. and Eugene Harbeck during a night whose events were clouded by booze, the mine had to be financed through stock sales that relied more on the reputation of surrounding properties than on anything that had been found on the Cresson property (MacKell, 2003). By 1908 the mine was $80,000 in debt. The owners hired Dick Roelofs, a heretofore unpromising engineer whose record didn't suggest that he would improve things; surprisingly, though, he did. Roelofs blossomed at the Cresson, finding ways to increase the efficiency of the mine and make a profit on relatively low-grade but abundant ore. By 1910, the mine was paying healthy dividends.
In November of 1914, something happened that would make the Cresson world-famous. On the 12th level, workers broke into a 4.5 × 8 × 13-meter cavity in altered breccia. Unlike most open cavities in the district, the Cresson vug was lined with crystals of calaverite. The gold telluride occurred as 1 to 3-mm free- standing crystals in solution cavities and as thin, fragile, leaf-like, deeply striated crystals to over 2.5 cm embedded in the less altered parts of the host rock (Patton and Wolf, 1915). Quartz (including chalcedony), dolomite and celestine were present, and the chamber lining contained a chalk-like, whitish material with abundant celestine, slightly altered calaverite and native gold. One notable characteristic of this occurrence was a lack of fluorite (Smith et al., 1985) and a scarcity of pyrite.
As noted by Smith et al. (1985), although specimens from the Cresson mine are not uncommon, documented material from the Cresson vug is very rare. This great rarity probably is a result of the tight security that accompanied removal of the contents of the vug. Vault doors guarded the mine entrance, and miners had to change clothes before leaving (MacKell, 2003). In a period of four weeks, about 1,400 sacks of ore (crystals scraped off the vug walls) were shipped out in sealed boxes protected by armed guards. The cavity yielded over 60,000 troy ounces of gold worth $1,200,000. Between 1903 and 1959, the once unpromising Cresson mine produced over $45,000,000 in gold. Present-day open-pit operations, which are centered on the Cresson mine, continue to yield about a quarter of a million ounces per year.
After Stratton sold the Independence mine, consolidation became the major theme for the district. First, more than one hundred mines were joined to form the United Gold Mines Company. This became a part of the Golden Cycle Mills Company in 1908. By building a modern, efficient cyanide mill in Colorado City in 1906, Golden Cycle took control of milling most of the district's mineral output.
Tunnel builder, railroad owner and freight hauler Albert "Bert" Carlton, with the backing of friends who owned the Utah Copper Company, and through a series of complicated maneuvers during the period from 1915 to 1931, gained control of all of the major Cripple Creek mills, railroads and mines, with the exception of the Portland and Strong mines (the Portland too joined Carlton's Golden Cycle Corporation, but only in 1933, after Carlton's death in 1931.)
In the mid-1930's, the price of gold rose from $20.67 to $35 per ounce, triggering a small boom in the district (Koschmann, 1947). At that time, 135 mines produced about $5 million in gold per year. Production through the early 1940's held steady at 125,000 to 145,000 ounces per year. Although production did not entirely cease during World War II, it was reduced to 30,000 to 45,000 ounces per year (Koschmann, 1947).
After the war, Golden Cycle started construction of the Carlton mill in order to save the cost of rail haulage to Colorado Springs. This triggered another small boom. In 1951, about 30 mines in the district produced over $2 million in gold. From then on, production significantly declined; in 1961 the Carlton mill closed, and in the following year the last mine in the district closed as well (Pontius, 1996). But Golden Cycle continued to acquire ground. By 1965 the corporation controlled 4,500 acres, approximately two-thirds of the district. In the mid-1970's, interest in gold properties increased sharply, following the "floating" of the U.S. dollar and the subsequent sharp rise in the price of gold. In 1976, Golden Cycle entered a 33:67 joint venture with Texasgulf Minerals, forming the Cripple Creek and Victor Gold Mining Company (CC&V). For the next 15 years, Texasgulf financed sporadic exploration in the district. In 1977, a junior company, Newport Minerals, began mining the Globe Hill breccia pipe in the north part of the district. All told, some 680,000 tons of ore were mined there (Trippel, 1985). This was followed shortly by the inauguration of Silver State Mining Company's open pit mine in the Ironclad breccia pipe.
Silver State is a very interesting company. It was founded and controlled by two brothers in their early 30's named Reid. Both were geologists, and both got their start working for Texasgulf in the district. They left Texasgulf. formed a company and, a few years later, acquired the Ironclad ground, after which they raised $3.5 million from the Denver equities market and put the property into production (Lewis, 1982). They mined out most of the breccia pipe (3.5 million tons averaging 0.06 oz/t Au). leaving an open pit with relatively small amounts of deep ore and steep high walls. This they were able to sell to Nerco Minerals for $3.5 million, plus the assumption of $4.5 million in debt (Business Week, 1985). The Reids then moved on to another successful venture at the Tomkin Spring gold deposit in eastern Nevada.
At about the time the Reids were operating at Ironclad, Texasgulf started heap-leaching the oxidized dumps scattered throughout the district. All told, some 3 million tons of dump material-most of the district's dumps-averaging 0.05 ounces of gold per ton, were processed. Texasgulf also started small-scale open-pit mines at the Portland mine and Pharmacist vein (in Altman) in 1988. Both pits were on the order of 500,000 tons, with ore averaging 0.07 ounces of gold per ton. These pits mined the newly discovered disseminated halos surrounding high-grade vein structures (Pontius, 1996). In 1989, Nerco bought out the Texasgulf interest in the Cripple Creek and Victor Gold Mining Company. In 1993, Independence Mining Company bought the Nerco interest and resumed mining at Ironclad and Globe Hill. Also at this time, the last major non-CC&V property was acquired by the company: CC&V now controlled 85 percent of the district. (On a personal note, the second author was at this time trying desperately and unsuccessfully to acquire the last major claim block for his employer. That prize proved to be quite significant-a considerable part of the present day reserves lie in that ground.) Design work for a new mega-pit centered on the old Cresson mine began in 1992, with permitting in 1993, construction in 1994, and first production in 1995 (AngloGold, 2001). In 1999, AngloGold acquired Independence Mining and its share of CC&V. AngloGold's new mega-pit was designed to exploit disseminated gold mineralization similar to that in the Altman and Portland pits. All told, an estimated 260 million tons of rock will be removed before mining ends-a far cry indeed from Bob Womack and his early attempts to generate any kind of interest in the district.
The Cripple Creek & Victor Gold Mining Co., which controls over 90 percent of the district today, is a joint venture between Pikes Peak Mining Co. (wholly owned by AngloGold North America) and Carlton's Golden Cycle Gold Corp. (CC&V, 1999). Thus, Carlton's legacy lives on at Cripple Creek, as elsewhere: the money that he and his friends made there and at Bingham Canyon financed businesses all over Colorado and the United States.
Within the western United States, a north-south-trending belt of alkaline igneous rocks extends from the Black Hills of South Dakota to the Capitan Mountains of New Mexico. Many of these rocks have associated gold deposits; examples include Annie Creek and Richmond Hill in South Dakota, Grayback in Colorado, and Elizabethtown-Baldy in New Mexico. But none of these deposits rivals Cripple Creek, whose estimated 25.5 million ounces of gold contained in a localized area less than 6 miles square constitutes some of the richest mineralized ground (in terms of dollar value) anywhere on the planet.
Central Colorado underwent major uplift during the Laramide Orogeny, a widespread compressive episode which took place between 70 and 40 million years ago. At this time, alkaline to calcalkaline intrusive activity occurred in the Colorado mineral belt (Kelley et al., 1996). During the Early Oligocene, extension came to dominate central Colorado, resulting in the formation of the Rio Grande rift. West of the Cripple Creek district, a north-striking horst-graben system that includes the Fourmile and Oil Creek faults (Wobus et al., 1976), along with dozens of other faults, was produced or reactivated at this time. Extension was accompanied by a resurgence of volcanism, as shown by the San Juan and 39-Mile volcanic fields (Lipman, 1981). These and similar volcanic rocks are parts of a gigantic volcanic episode in the western U.S. and northern Mexico that generated some 500,000 km^sup 3^ of ignimbrites and up to 5,000,000 km^sup 3^ of intermediate to silicic magmas (Johnson, 1991).
Extension associated with the Rio Grande rift provided the impetus for igneous activity over a large part of the interior of the western U.S. As the rift began to open in the Oligocene, confining pressure was reduced in the underlying mantle, resulting in pressure-release melting and formation of a volatile-rich, alkaline magma (Wilson, 1989; Kelley et al., 1996). As it moved upward, the parent magma assimilated lower crustal rocks and underwent fractional crystallization (Birmingham, 1987). Apparently, the magma rose rapidly enough so that it suffered little contamination hy upper crustal rocks (Kelley et al., 1996). Faults and shear zones in Proterozoic rocks provided local pathways for migration of magma and volatiles, once they reached the upper crust.
During and after the first shallow intrusions, the magma body underwent further differentiation, its upper parts becoming enriched in water, carbon dioxide, chlorine, sulfur, arsenic, bismuth, molybdenum and antimony (Kelley et al.. 1996). At this point, a feedback-loop process as described by Burnham (1985) probably took over, contributing to the formation of the brecciated host rocks of Cripple Creek's gold deposits. In this process, as water-saturated melts move upward, the decreasing pressure allows water-rich fluids to expand, which, in turn, yields mechanical energy. At depths of 10 to 8 km or less, the pressure of escaping fluids may exceed the strengths of common wall rocks. The wall rocks fractured, which further reduced pressure on the confined fluids. In the resulting feedback loop, more water then came out of solution, generating more fractures. Increasing effervescence at depth combined with gas streaming and fluidization of the shattered rock may propel wall-rock fragments for hundreds of meters upward (Burnham, 1985).
The Cripple Creek mining district occupies a composite Oligocene volcanic-sedimentary subsidence crater (diatreme) associated with subsilicic alkaline rocks. The diatreme formed between 33 and 28 million years ago (Kelley et al.. 1996). roughly synchronous with the onset of extension in Colorado. The district is centered over a gravity and magnetic low that suggests the presence of a batholithic body at depth (Kleinkopf et al., 1970). The diatreme occurs at the intersection of four Precambrian granite and gneiss units and is centered on a compressionally formed Laramide-age dome. There appears to have been an ancestral structural weakness in the area that focused igneous and mineralizing activity. Present exposures are at the subvolcanic level; any traces of a tuff ring or maar have been eroded off. Remnants of the volcano form a group of rounded hills that range between about 3170 and 3570 meters in elevation.
The diatreme consists of a large mass of breccia intruded by bodies of phonolite, plagioclase phonolite (historically called latite phonolite), tephriphonolite (historically called syenite), and lamprophyre (historically called alkali basalt) (Kelley, 1996; Pontius, 1996). The breccia, with a surface exposure of roughly 18 square kilometers, fills an irregular basin up to 1 km deep that contains three separate sub-basins. Previously, each sub-basin was interpreted as a separate vent area; present interpretations are that there were multiple vents associated with a central, northwest-trending fissure zone (which is also the main mineralized trend), as well as discrete lesser vents at local structural intersections (Pontius, 1996).
In cross-section, the Cripple Creek breccia body flares outward toward the surface, with the deepest part centered on the Cresson "blowout" (Thompson etal., 1985). The basin's walls generally dip inward at 65° to 80° and are irregularly configured, with local overhangs, especially in the southwest (Koschmann. 1949). At the Ironclad and other mines, microbreccias show evidence of subsurface fluidization, including channeling, graded bedding, and flow around large clasts (Seibel, 1996). Mineralized pipe-like breccia bodies formed by explosive activity occur in the south-central part of the complex (the Cresson "blowout" of Loughlin and Koschmann, 1935) and in the North basin (Ironclad mine; Seibel, 1996). In places, the basin also contains intact, deeply buried fluvial and lacustrine sedimentary rocks with mudcracks. raindrop imprints, bird tracks, and plant fossils. Such sedimentary rocks were found at great depths within the mines, supporting the idea that the basin owes its origin mostly to intermittent subsidence (Koschmann, 1949).
Although sediments and breccia pipes are important components of the basin, the main fill materials are breccias. The fill resulted from repeated mild deformation and brecciation, subsidence and consolidation of the brecciated rock, and recurrent explosive volcanic eruptions (Gott et al., 1969). Typically, the breccia consists of poorly sorted clasts of phonolite, phonolite tuff and granitic country rock within a tuff matrix. The breccia was intruded by a series of plugs, domes, flows, dikes and sills of varying alkaline subsilicic composition. Gold mineralization was one of the latest events, but minor igneous activity producing lamprophyre dikes continued before and after. Some breccia-dike activity appears to have followed emplacement of the lamprophyre dikes, and there is some controversy with regard to whether gold in the breccia dikes represents introduction of new gold mineralization or just reworking of previously deposited gold (Seibel, 1991, 1996; Thompson, 1996).
Within the district, major faults are rare. Rather, the area is characterized by a series of slips and fractures with minimal displacement. Typically, relatively short individual veins define long, narrow ore runs. Well formed, strongly outcropping veins were not the norm at Cripple Creek. Instead, there were sheeted zones of subparallel fractures, particularly in hard, brittle rocks such as the phonolite. (Within the breccia, the veins were much more anastomosing and irregular.) When hosted by the Proterozoic rocks that encircle the basin, the veins exhibit a radial pattern. Within the basin they generally trend northwest or northeast, and most dip at angles of 75° or more. Because quartz is typically only a minor constituent of the veins (where it is present at all), the sheeted zones and veins did not crop out prominently; as a result, gold was discovered much later here than elsewhere in Colorado.
Ore runs at Cripple Creek typically strike in directions between northwest and northeast but are centered on a master northwesttrending zone that runs through the approximate center of the diatreme. This zone extends through the gold-breccia body at Carbonate Hill (at the far northern end of the diatreme), and through the breccia pipes at Ironclad, Globe Hill and Cresson, ending at the Portland mine at the southern end of the diatreme. In addition, there are several subparallel splits in the southern portion of the district; famous mines such as the Vindicator, Last Dollar and Victor exploited these.
Cripple Creek ore concentrations are of three major types: (1) narrow, high-grade gold/silver telluride veins; (2) broad zones of low-grade disseminated native gold/pyrite; and (3) breccia pipes, in which disseminated gold and tellurides occur primarily in clasts, and with widespread associated sericitization/argillization (Pontius, 1992; Burnett, 1995; Seibel, 1996). All three types are hydrothermal in origin.
The vein deposits were found first and were the richest in metal values, commonly containing concentrations of 0.5 to 2 ounces of gold per ton. The veins exhibited minimal changes in ore grade as mining continued to depths of more than 1000 meters, although with increasing depth the veins grew thicker and fewer, i.e. vein density expanded upwards in a pattern resembling the branching of a tree. The distribution of gold and other elements suggests that mineralizing solutions worked their way upward and outward from a few deep-seated fissures (Gott et al., 1969).
The disseminated mineralization consists of microscopic native gold, commonly attached to pyrite and associated with fine-grained orthoclase ("adularia"). This material occurs as an alteration halo surrounding the high-grade vein structures, particularly at vein intersections. Disseminated deposits occur in the upper 300 meters of the diatreme complex, and contain gold concentrations measured in hundredths of an ounce per ton. This type of ore is the target of present-day mining. Today, exploration consists of plotting historic vein workings and testing their perimeters for the disseminated gold halo. In order to do this, a truly phenomenal GIS database has been constructed by AngloGold.
The third type of mineralization is associated with breccia pipes. Here, the gold (which occurs as native gold and in tellurides) is accompanied by orthoclase, fluorite, dolomite, and pyrite, the same general mineral assemblage as in the veins. The Carbonate Hill breccia pipe also contains molybdenite and hiibnerite. Rarely, native gold coating hubnerite has been observed at this locality. Native gold that occurs in the breccia pipes is considered to be both hypogene and supergene (derived from the oxidation of tellurides) in origin and can be quite coarse. Breccia pipes also contain celestine, hematite, barite, anhydrite, and manganese oxides. Widespread sericitization/argillic alteration is associated with breccia pipes but is not seen in the vein deposits.
Thompson (1996) interpreted the breccia pipes as the shallow-level equivalents of vein systems. Local blockage by earlier mineralization or by late sills may have allowed pressure to build until it exceeded lithostatic pressure to depths of as much as 1000 m. This caused brecciation of the wall rock and boiling of the ore fluid. The resulting hydrothermal breccias were localized along pre-existing zones of weakness (Thompson et al., 1985).
Recent work has helped to clarify the origin of the ores and the physical conditions of their formation. At the time of ore formation, temperatures were less than 200°C (Thompson et al., 1985; Saunders. 1988; Seibel, 1996). Data from fluid inclusions show that ore-fluid salinities decreased with time, and that near-surface fluids were less saline than deeper fluids at the time of gold deposition (Thompson, 1996). The high initial salinity and oxygen-isotope data support the idea that the fluids came from a magmatic source (Kelley, 1996); also, isotopic data suggest a mantle source for sulfur and a crustal source for lead and, possibly, gold (Fears el al., 1986). The compositions of the ore, gangue, and alteration mineral assemblages, supported by observations of geochemistry and field relations, support the theory that the hydrothermal activity was most closely related to the lamprophyre dikes and breccias. These mafic rocks generally contain higher gold concentrations than other possible source rocks in the district.
Thompson (1996) suggests that the deeper hydrothermal veins and shallow disseminated deposits represent the extreme ends of a continuum of fluid evolution. As they ascended, the fluids became more oxidized. At depth, the fluids were alkaline, becoming neutral or weakly acidic near the surface. Oxidation of H^sub 2^S near the surface produced sulfate anions, which combined with magmatic Ca and Sr to produce anhydrite and celestine respectively (Thompson, 1996; Thompson et al., 1985). Abundant CO2 in the fluids resulted in abundant carbonates in the gangue. Pyrite and minor base-metal sulfides (enargite, galena, sphalerite, tetrahedrite) formed where H^sub 2^S was not oxidized. Gold and tellurium enrichment occurred in the later stages of vein formation, after deposition of orthoclase, fluorite, dolomite, and pyrite.
Aqueous tellurium complexes may have transported the gold (Saunders, 1988). Gold is relatively soluble as AuTe, complexes in the temperature range indicated by fluid-inclusion studies of the Cresson and other deposits. AuTe^sub 2^ complexes would have been precipitated by oxidation, with native gold deposition following telluride precipitation (Saunders, 1988; Thompson, 1996). In contrast, under neutral to slightly alkaline pH (as implied by the presence of sericite and orthoclase) and oxidizing conditions, gold should be relatively insoluble as bisulfide or chloride complexes. Interestingly, the lack of any significant change in gold content upward in the veins suggests that temperature gradients had no major effect on the deposition of gold or gold tellurides.
All workers agree that mineralization occurred in several stages, but there is some disagreement about the details. Loughlin and Koschmann (1935) and Gott et al. (1969) recognized three stages of mineralization. Stage I includes deposition of quartz, orthoclase, dark purple fluorite, coarse pyrite, and minor specular hematite. This stage corresponds with intense alteration of the country rock. Stage II includes deposition of milky to smoky quartz, pale purple fluorite, fine-grained pyrite, specular hematite, dolomite or ankerite, celestine, barite, roscoelite, sphalerite, galena, tetrahedrite, calaverite, krennerite, sylvanite, petzite, hessite, and native gold. Stage III minerals include smoky to colorless quartz, yellowish to orange chalcedony, fine-grained pyrite, calcite, cinnabar, and minor fine-grained fluorite.
Thompson (1996) posited five stages of mineralization for major veins at Cripple Creek and summarized corresponding fluid temperatures determined by various workers. His vein sequence is as follows:
Stage I: feldspar + quartz + fluorite + dolomite + pyrite + marcasite
Stage II: pyrite/marcasite + galena + sphalerite + chalcopyrite
Stage III: specular hematite + quartz + fluorite + pyrite + rutile
Stage IV: quartz + pyrite + tellurides
Stage V: vug-filling quartz/chalcedony + fluorite + dolomite.
Thompson (1996) also recognized three stages of mineralization in diatreme (e.g. Cresson mine) and hydrothermal breccia (e.g. Ironclad and Globe Hill mines) deposits:
Stage I: feldspar + quartz + apatite + pyrite/marcasite + fluorite + hematite
Stage II: celestine + sericite + dolomite + barite + galena + sphalerite + chalcopyrite + fluorite + pyrite + quartz + rutile
Stage III: tellurides + pyrite + dolomite + quartz + sericite + native gold + Fe, Mn oxides.
Further, Thompson (1996) summarized the vertical distribution of common minerals in the Cripple Creek hydrothermal system. Major veins occur throughout the 1000-meter vertical range that has been explored. Hydrothermal breccias are relatively shallow systems, and the Cresson diatreme extends from the surface to moderate depth. Native gold, chalcedony, sulfates, stibnite, cinnabar, Fe and Mn oxides, sericite, and smectite all occur at shallow to moderate depths. Roscoelite is confined to deeper deposits; orthoclase, carbonates, fluorite, galena, pyrite, sphalerite, specular hematite, tellurides, quartz, and marcasite occur over the whole range of depths that have been studied. These zoning features are quite subtle; what stands out is the relative consistency of grades and mineralization over thousands of vertical feet of workings.
Pontius (1996) summarized a more detailed depositional model that combines the work of several colleagues. It starts with an initial stage of high-temperature, high-salinity hydrothermal activity that coincided with decreasing volcanism (Dwelley, 1984). This stage coincided with a period of resurgent phonolite doming when the fluids associated with doming, although essentially barren, created extensive zones of permeability. During a second stage, episodic, low-temperature, low-salinity (Reynolds, 1992) hydrothermal activity occurred over a period of about 2 million years. Potassium metasomatism, represented mainly by sericite and orthoclase, and pyritization are common features of this event; this is also the time of both gold telluride and disseminated native gold deposition. The last stage was characterized by the formation of the hydrothermal breccia pipes in which mineralization is almost entirely confined to clasts. This stage corresponds with emplacement of lamprophyre intrusives that marks the end of igneous activity (Pontius, 1996).
Supergene alteration caused by descending sulfate-bearing waters derived from the decomposition of nearly ubiquitous pyrite bleached the breccia, granite, and "dikes" near the largest and most persistent mineralized zones (Loughlin and Koschmann, 1935). Calcite and dolomite were dissolved in places, and analcime, sodalite, nepheline, and feldspars in the phonolitic host rocks were locally altered to clay. In basaltic rocks, secondary zeolite minerals resulted. Some iron in solutions from near the surface formed secondary pyrite or marcasite by reduction at depth. In other places, the iron formed green, iron-rich clay (nontronite). In the ores, oxidation and interaction with meteoric water leached tellurium, leaving gold pseudomorphs after telluride minerals. In such cases, the gold may be embedded in a soft mass of iron-stained quartz and clay with fluorite and celestine. The tellurium may form "green oxide" (Loughlin and Koschmann, 1935) (the mineral emmonsite?). Rare occurrences of crystallized and wire gold probably result from redeposition of gold dissolved near the surface.
More than 120 minerals have been identified in rocks from the Cripple Creek district. Although relatively few of these are of collector interest, a complete listing of reported species has not been available until now; such a listing, as presented here, should be of use to Colorado collectors.
Mineral specimens from the Cripple Creek district are rarely flashy or even attractive. To the casual collector, the ores resemble pyrite, marcasite, or arsenopyrite. The fact that pyrite is nearly ubiquitous complicates matters for those unfamiliar with the ore minerals. Even well crystallized specimens of the major telluride ore minerals are notoriously difficult to distinguish in hand specimen; more sophisticated analytical techniques are required for their certain identification.
Because of the district's fame, the lack of large numbers of spectacular specimens, and the absence of specific locality information to accompany many specimens, some dealers and collectors have exercised more than a little imagination in their attributions. If a specimen obviously came from Cripple Creek but information on the particular mine was lacking, some apparently have felt safe in claiming that the specimen came from the famous Cresson mine. The senior author has seen (and, in his early years, purchased) specimens with fanciful labels detailing where and when specimens were collected and by whom, only to find that they were not even from North America. Such specimens are well known to Colorado specialists, but others may lack the background to recognize them for what they are. Let the gullible beware. On the other hand, the occasional spectacular melonite specimen that reaches the market most likely really did come from the Cresson mine. The almost equally uncommon groups of distinctive, large amethyst crystals found in many museum collections certainly originated in the district, but the exact locality is at this time unknown to the authors. The provenance of many of the telluride specimens can be recognized by their associations and by the characteristics of the host rock. If you are interested in Cripple Creek minerals, don't despair. As always, learn all you can and be skeptical of offerings that seem too good to be true.
In the following treatment, the minerals are listed alphabetically. Each is placed into at least one of five categories: rock-forming minerals (R); ore minerals (O); gangue minerals (G); alteration minerals (A); and supergene minerals (S). Rock-forming minerals are subdivided into two categories: essential (RE) or accessory (RA) minerals. Similarly, ore and gangue minerals are classified according to their occurrence in vein deposits (OV or GV) or in disseminated deposits (OD or GD). Alteration minerals may occur in veins (AV), in disseminated deposits (AD), or in the host rocks (AH). Finally, supergene minerals may occur in the oxidized zone (SO) or in the zone of supergene sulfide enrichment (SS). Brief descriptions are included for each mineral, with more information on those of collector interest.
Acanthite Ag^sub 2^S (OV)
Acanthite is a minor late-stage vein mineral, reported at the Ajax mine and elsewhere and with gold and jarosite in oxidized outcrop samples (Thompson, 1992; Thompson et al., 1985; Hildebrand and Gott, 1974).
Actinolite Ca^sub 2^(Mg, Fe^sup 2+^)^sub 5^Si^sub 8^O^sub 22^(OH)^sub 2^ (RE)
Actinolite is abundant in schist in a railroad cut west of Victor (Eckel, 1997).
Adularia See orthoclase.
Aegirine; Aegirine-Augite NaFe^sup 3+^Si^sub 2^O^sub 6^ (RA)
Aegirine is common in all Oligocene intrusive rocks of the district. It occurs as phenocrysts in plagioclase phonolite; as acicular, prismatic and blunt crystals in phonolite, where it may occur included in analcime or in sheaves of acicular crystals wrapped around nepheline; as small crystals in phonotephrite; as a constituent of lamprophyre dikes; and as phenocrysts in tephriphonolite (Loughlin and Koschmann, 1935; Thompson et al., 1985; Lindgren and Ransome, 1906; Birmingham, 1987).
Allanite (undivided) (RA)
Allanite occurs as an accessory mineral in the Cripple Creek "granite" (Lindgren and Ransome, 1906).
Allaite PbTe (OV: OD)
Altaite is uncommon, occurring at the Cresson mine as silvery white massive ore (Saunders, 1988; Geller, 1993).
Alunite K^sub 2^Al^sub 6^(SO^sub 4^)^sub 4^(OH)^sub 12^ (SO)
Alunite is described as hard, compact, fine-grained, kaolin-like masses in the oxidized veins of the Last Dollar and Modoc mines (Lindgren and Ransome, 1906).
Alunogen Al^sub 2^(SO^sub 4^)^sub 3^.17H^sub 2^O(SO)
Admixtures of alunogen and epsomite are reported, with no details (Eckel, 1997).
Analcime NaAlSi^sub 2^O^sub 6^-H2O (RE)
Analcime is a common constituent of all of the Oligocene rocks of the district, including phonolite, plagioclase phonolite, phonotephrite, tephriphonolite, vogesite, and monchiquite It occurs as drusy crystals in cavities, as irregular masses, as phenocrysts, and surrounding nepheline crystals (Lindgren and Ransome, 1906; Loughlin and Koschmann, 1935; Birmingham, 1987).
Ancylite-(Ce) SrCe(CO^sub 3^)^sub 2^(OH).H2O (RA)
Ancylite-(Ce) is described by Birmingham (1987) as grains less than 15 µm in phonolite.
Andradite Ca^sub 3^Fe^sub 2^(SiO^sub 4^)^sub 3^ (RA)
Andradite occurs as zoned crystals (Standish, 1971).
Anglesite PbSO^sub 4^ (SO)
Anglesite resulted from alteration of galena by oxygenated meteoric water at the Gold Hill mine (Thompson et al., 1985).
Anhydrite CaSO^sub 4^ (GD)
Anhydrite is described as a late-stage gangue mineral in the matrix of the hydrothermal breccias at the Gold Hill mine (Thompson etal., 1985).
Ankerite Ca(Fe^sup 2+^,Mg,Mn)(CO^sub 3^)^sub 2^ (CV)
Ankerite occurred as small, white, rhombic middle-stage crystals in vugs in plagioclase phonolite and in the wall rock of the Gold King and other mines (Lindgren and Ransome, 1906; Loughlin and Koschmann, 1935).
Anorthoclase (Na,K)AlSi^sub 3^O^sub 8^ (RE)
Anorthoclase is a constituent of phonolite, restricted to groundmass (Birmingham, 1987).
Apatite Group (undivided) (RA; CV; GD)
Apatite-group species occur as gray, euhedral, prismatic crystals in extremely porphyritic plagioclase phonolite: as minor constituents in phonolite, tephriphonolite, phonotephrite, lamprophyre, and in Proterozoic rocks, including Pikes Peak Granite, Cripple Creek "granite," gneiss, and schist; in hydrothermal veinlets in the host rocks; as early to middle-stage alteration minerals in the hydrothermal breccias at the Gold Hill mine; and in slender micro-prisms, as abundant secondary minerals with orthoclase at the Elkton mine (Lindgren and Ransome, 1906; Loughlin and Koschmann, 1935; Thompson et al., 1985; Thompson, 1992).
Arfvedsonite Na^sub 3^(Fe,Mg)^sub 4^FeSi^sub 8^O^sub 22^(OH)^sub 2^ (RA)
Needles and microscopic stout prisms of arfvedsonite occur in phonolite (Lindgren and Ransome, 1906; Birmingham, 1987).
Arsenopyrite FeAsS (GV)
Lindgren and Ransome ( 1906) report arsenopyrite from the Ajax mine.
Autunite/Meta-autunite Ca(UO^sub 2^)^sub 2^(PO^sub 4^)^sub 2^.2-6H^sub 2^O (SO)
Autunite has been reported as a very minor supergene mineral produced by weathering of alteration products of early- stage veins at the Globe Hill mine, and associated with other secondary uranium minerals in Tertiary volcanics (Thompson et al., 1985; Young and Mickle, 1976; Nelson-Moore et al., 1978).
Baddeleyite ZrO, (RA)
Birmingham (1987) reported baddeleyite as very small crystals in the groundmass of a phonotephrite dike at the Isabella mine.
Barite BaSO^sub 4^ (GV; GD)
Barite is a middle-stage mineral, occurring as massive aggregates and small crystals in the El Paso and Portland veins and commonly intergrown with tellurides at the Cresson mine (Lindgren and Ransome, 1906; Loughlin and Koschmann, 1935; Saunders, 1988; Thompson, 1992). Barite commonly has been confused with celestine.
Biotite K(Mg,Fe)^sub 3^(Al,Fe)Si^sub 3^O^sub 10^(OH,F)^sub 2^ (RA; GV)
Biotite occurs as phenocrysts or as a minor groundmass constituent of all Cripple Creek volcanics and most Proterozoic host rocks. It also occurs with apatite and pyrite in hydrothermal veinlets penetrating the host rocks and in the Dolly Varden vein (Lindgren and Ransome, 1906; Loughlin and Koschmann, 1935; Thompson et al., 1985; Thompson, 1992).
Boulangerite Pb^sub 5^Sb^sub 4^S^sub 11^ (OV)
Boulangerite may occur as irregular grains enclosed in bournonite from the El Paso mine (Lane, 1976).
Bournonite PbCuSbS, (OV)
Bournonite is reported as rims around galena grains and associated with tetrahedrite-tennantite from the El Paso mine (Lane, 1976).
Cacoxenite (Fe,Al)^sub 25^(PO^sub 4^)^sub 17^O^sub 6^(OH)^sub 12^.75SH^sub 2^O (SO)
Cacoxenite is locally common in fractures in dump samples from the John A. Logan mine, where it occurs as acicular crystals to 0.3 mm in radially intergrown mats covering areas of several square cm. It occurs in partly oxidized gray orthoclase-quartzpyrite rock, following earlier strengite and followed by an unidentified green member of the rockbridgeite family (Eckel, 1997).
Calaverite AuTe^sub 2^ (OV; OD)
Calaverite is the most common telluride in the district, occurring as a late middle-stage vein mineral (Loughlin and Koschmann, 1935; Thompson et al., 1985) and as a minor stage-two (of four) mineral of disseminated deposits at Globe Hill (Thompson et al., 1985). It occurs as silvery white to pale yellowish, flat to slender, striated, prismatic crystals, commonly to several mm, in vugs; and as thin, bladed crystals to 20 cm, some in radial aggregates. In places, calaverite is intergrown or associated with other vein minerals (chalcedony, fluorite, celestine, pyrite, stibnite, etc.) (Lindgren and Ransome, 1906; Patton and Wolf, 1915). Less commonly it is massive. At Cresson, calaverite crystallization overlaps but has primarily occurred after the crystallization of base-metal sulfide minerals, and in some cases it is replaced by petzite, melonite and altaite (Saunders, 1988). It commonly is coated and obscured by later vein minerals, especially chalcedony. In oxidized deposits, calaverite may be partly replaced by native gold and rusty-looking iron oxides. In the past, a common practice was to call yellowish telluride minerals calaverite and to call silvery tellurides sylvanite. However, the physical properties of both minerals are variable, and analytical work is necessary for certain identification.
Calcite CaCO^sub 3^ (GV; AH)
Calcite is uncommon in veins, occurring as colorless to white, rarely yellow, scalenohedrons formed in the middle stage of mineralization. It also occurs as a minor alteration product in plagioclase phonolite and Ca-rich lamprophyre (Loughlin and Koschmann, 1935).
Celadonite KFe^sup 3+^(Mg,Fe^sup 2+^)[white square]Si^sub 4^O^sub 10^(OH)^sub 2^
Birmingham (1987) described celadonite in vesicles and cracks in volcanic breccia and altered tephriphonolite.
Celestine SrSO^sub 4^ (GV; GD)
Celestine occurs as an early-stage vein mineral (Loughlin and Koschmann, 1935) of the disseminated deposits at Globe Hill (Thompson et al., 1985). It is also found in vein fragments and as a gangue mineral in hydrothermal breccias, and occurs as small, white, bluish, or bright yellow slender prisms or needles coating the walls of vugs in veins. It commonly is intergrown with tellurides at Cresson and other mines, and is associated with "limonite," kaolinite and native gold in oxidized veins. It may be coated or replaced by quartz, and in some cases dissolved out, leaving hollow quartz coatings sometimes labeled as "quartz after stibnite" (Lindgren and Ransome, 1906). At the Cresson open pit, celestine collected in 2001 occurred as bluish, white or yellow prisms to 2.5 cm associated with creedite, rhodochrosite and gearksutite. It also has been described as an accessory mineral in monchiquite and gray plagioclase phonolite (Birmingham, 1987).
Chalcanthite CuSO^sub 4^.SH^sub 2^O (SO)
Chalcanthite was scarce in oxidized veins at the Gold King and Lone Jack mines and in the Ophelia, Chicago, and Cripple Creek tunnels (Lindgren and Ransome, 1906).
Chalcocite Cu^sub 2^S (OV)
Chalcocite was questionably identified from the Uncle Sam mine (Lindgren and Ransome, 1906).
Chalcopyrite CuFeS^sub 2^ (OV; OD)
Chalcopyrite was locally abundant at the Cresson mine (Saunders, 1988). It occurred as a stage-three (of five) vein mineral and in stages 1, 2 and 4 (of 4) in breccias at Globe Hill (Thompson et al., 1985). Lindgren and Ransome (1906) describe rare thin coatings of Chalcopyrite on tetrahedrite at the Blue Bird mine.
Chlorite Group (undivided) (AH; AD; AV)
Chlorite formed by alteration of biotite and/or amphibole in most rocks of the district, including veins and breccias (Lindgren and Ransome, 1906; Thompson et al., 1985; Thompson, 1992).
Chrysocolla (Cu,Al)^sub 2^H^sub 2^Si^sub 2^O^sub 5^(OH)^sub 4^.nH^sub 2^O (SO)
Lindgren and Ransome (1906) reported chrysocolla as a product of oxidation of tetrahedrite at the Ironclad mine.
Cinnabar HgS (OV)
Cinnabar was a widespread but rarely obvious stage-3 mineral in veins and in open breccias in the Dante mine (Loughlin and Koschmann, 1935; Eckel, 1997). It occurred as disseminated coatings on pyrite and as small botryoidal druses in vugs. With other species, it may coat tellurides. Cinnabar also occurred with native mercury at the Moon Anchor mine (Lindgren and Ransome, 1906).
Coloradoite HgTe (OV)
Coloradoite has been reported from the Moon Anchor mine (with native mercury) and Clara D claim (Gold Hill) (Eckel, 1997), and intergrown with galena and krennerite and associated with acanthite and jarosite at the Cresson mine (Hildebrand and Gott, 1974).
Copper Cu (AH)
Lindgren and Ransome reported a single specimen of native copper in an oxidized lamprophyre dike on Mineral Hill, possibly derived from oxidation of tetrahedrite. It was also found when sinking the shaft for the Logan mine (Bancroft, 1903).
Corkite PbFe^sub 3^(PO^sub 4^)(SO^sub 4^)(OH)^sub 6^ (SO)
Corkite occurred at the John A. Logan mine, as thin, shiny plates to 0.3 mm intergrown to form irregular rosettes coating vug walls in comb quartz and associated with pyrite, fluorite, and tetrahedrite (Eckel, 1997).
Corundum Al^sub 2^O^sub 3^ (RA)
Corundum was described by Lindgren and Ransome (1906) as occurring in Proterozoic sillimanite schist south of Red Mountain.
Covellite CuS (SS)
Covellite has been reported as a supergene mineral formed by alteration of chalcopyrite and as distinct, minute grains associated with other copper sulfides (Lane, 1976; Thompson et al., 1985).
Creedite Ca^sub 3^Al^sub 2^(SO^sub 4^)(F,OH)^sub 10^.2H^sub 2^O (GD)
Creedite was first found at Cripple Creek in the Cresson open pit in 2001, as colorless/white to pale and medium purple aggregates of small (to 1 cm), radiating crystals associated with blue, white and yellow celestine, gearksutite, cubic pyrite and botryoidal rhodochrosite. Gearksutite generally is the last of these minerals to form (D. Bunk, personal communication). Some specimens show celestine intergrown with or overlying creedite.
Crossite Na^sub 2^(Mg,Fe)^sub 3^(Al,Fe)^sub 2^Si^sub 8^O^sub 22^(OH)^sub 2^ (RA)
Blue amphibole found in some Cripple Creek volcanic rocks is allied to crossite (Cross and Penrose, 1895; Birmingham, 1987).
Dolomite CaMg(CO^sub 3^)^sub 2^ (GV; GD; AH)
The most widespread (but seldom obvious) carbonate of veins and wall rocks, dolomite occurs as small, white to greenish, rhombohedral crystals in altered breccia and intrusives, as crusts in veins, as an alteration product in wall rocks, where it replaces biotite and analcime and permeates margins of felsic rock fragments, and as a cementing material of breccia and tuff host rocks (Loughlin and Koschmann, 1935; Thompson, 1992). It also formed hollow pseudomorphs, where coated by opal (Lindgren and Ransome, 1906). It preceded and overlapped the occurrence of calaverite at the Cresson mine (Saunders, 1988).
Emmonsite Fe^sub 2^Te^sub 3^O^sub 9^.2H^sub 2^O (SO)
Emmonsite is a green oxide of tellurium deposited as a result of alteration of tellurides by meteoric water (Loughlin and Koschmann, 1935). As small, often mammillary yellowish green masses, emmonsite occurs with native gold, tellurite and partially oxidized calaverite (Lindgren and Ransome, 1906; Eckel, 1997). Emmonsite has been reported from the WPH, Moose and Deadwood mines.
Enargite Cu^sub 3^AsS^sub 4^ (OV)
Enargite is reported as minute grains in tetrahedrite, bournonite, and sphalerite at the El Paso mine (Lane, 1976).
Epidote Ca^sub 2^Al^sub 2^(Fe^sup 3+^,Al) Si^sub 3^O^sub 12^ (OH) (AH)
A widespread alteration mineral found in Proterozoic granite, schist, and gneiss, epidote has also been reported in lamprophyre, plagioclase phonolite, and tephriphonolite (Lindgren and Ransome, 1906; Thompson, 1992).
Epsomite MgSO^sub 4^.7H^sub 2^O (SO)
Epsomite occurred as secondary encrustations where ground water emerged into openings (Loughlin and Koschmann, 1935). It was reported from the 1000 level of the Portland mine, where it was mixed with other sulfates (Lindgren and Ransome, 1906).
Fayalite Fe^sub 2^SiO^sub 4^ (RA)
Gross (1962) reported the occurrence of fayalite in an "augite syenite."
Ferrimolybdite (?) Fe^sub 2^(MoO^sub 4^)^sub 3^.8H^sub 2^O (SO)
Ferrimolybdite or a closely related mineral occurred on the north side of Battle Mountain as bright yellow, capillary crystals in cracks and joints of weathered plagioclase phonolite, and with ilsemannite as an alteration product of molybdenite in a vein exposed in the Ophelia tunnel (Lindgren and Ransome, 1906; Eckel, 1997).
Fluorite CaF^sub 2^ (GV; CD; AH: RA)
Fluorite is an extremely common species (but rarely found in aesthetic specimens) in almost all stages of mineralization of both vein and disseminated deposits, in sedimentary-hosted deposits, in the oxidized zone with free gold, as fragments in breccia, replacing biotite in some host rocks, and as a minor primary mineral in the granitic host rocks (Lindgren and Ransome, 1906; Loughlin and Koschmann, 1935; Thompson et al., 1985; Thompson, 1992). In the veins, it occurred mostly as purple cubic crystals, less than 5 mm, coating vugs and crevices with quartz and dolomite. At the Cresson mine, it formed bright yellow, cubic crystals to 2 cm (Eckel, 1997), with quartz. Birmingham (1988) reported tiny purple crystals enclosed in sodalite and nosean in the Tertiary intrusives.
Forsterite Mg^sub 2^SiO^sub 4^ (RE)
Forsterite occurs as phenocrysts to 1 cm in the lamprophyre dikes (monchiquite and vogesite) and as small grains, some serpentinized or altered to "iddingsite," in phonolite, phonotephrite, and tephriphonolite (Lindgren and Ransome, 1906; Loughlin and Koschmann, 1935; Birmingham, 1987; Thompson, 1992).
Galena PbS (OV; OD)
Galena was locally conspicuous as an early component of hydrothermal breccias and veins, with other base-metal sulfides. It was especially abundant in the western part of the district, where it occurred in veins and in the oxidized zone, in which it had altered to anglesite and cerussite (Thompson et al., 1985).
Gearksutite CaAl(OH)F^sub 4^.H^sub 2^O (GD)
Gearksutite was first found in the Cresson open pit in 2001. It occurs as small, white, irregular vug-filling masses and as colliform aggregates to several cm with orange botryoidal rhodochrosite, bluish, white, or bright yellow celestine and colorless to purple creedite. Gearksutite is the last mineral to form in this assemblage (D. Bunk, personal communication). It resembles kaolinite and may have been misidentified as such in the past.
Goethite α-Fe^sup 3+^O(OH) (SO)
Goethite is a supergene mineral, formed by weathering of alteration products and vein minerals by oxidizing water at the Globe Hill mine (Thompson et al., 1985) and elsewhere.
Gold Au (SO; OD; OV)
Gold is uncommon as large grains, spongy masses, thin sheets, plates and grooved pseudomorphs after calaverite and other tellurides. It is commonly found coated by iron oxides and associated with iron-stained quartz and clay with minor to abundant celestine and fluorite (Lindgren and Ransome, 1906; Loughlin and Koschmann, 1935). Gold in the oxidized zone may be so coated with iron oxides that it is, at first glance, nearly invisible. Grains or wires of free gold, pea-sized clusters of gold crystals, and cubic crystals to 2 cm have been described (Eckel, 1997). Some of these are associated with tellurides in hypogene deposits. At the Cresson open pit, disseminated microcrystalline native gold attached to pyrite is associated with orthoclase in permeable host rocks adjacent to major structures (Pontius, 1996). The Carbonate Hill breccia pipe contains hübnerite which, on rare occasion, is found coated by gold.
Greenockite (?) CdS (OV)
Dark brown sphalerite in the Last Dollar mine contained much cadmium, possibly as greenockite inclusions or coatings (Lindgren and Ransome, 1906).
Gypsum CaSO^sub 4^.2H^sub 2^O (SO; AD; AH; AV)
Gypsum occurred in large masses associated with fluorite and pyrite in the Deerhorn mine and was widespread in oxidized ores, where it resulted, in part, from hydration of anhydrite. It also formed secondary encrustations where groundwater emerged into open spaces (Lindgren and Ransome, 1906; Loughlin and Koschmann, 1935; Thompson et al., 1985).
Hauyne (Na,Ca)^sub 4-8^Al^sub 6^Si^sub 6^(O,S)^sub 24^(SO^sub 4^,Cl)^sub 1-2^ (RA)
Haüyne is common in small quantities as phenocrysts in phonolite and monchiquite (Loughlin and Koschmann, 1935; Birmingham, 1987).
Hematite α-Fe^sub 2^O^sub 3^ (GV; GD; RA; AH; SO)
Specular hematite occurs in small vugs in plagioclase phonolite and in cleavages in microcline in the Pikes Peak Granite. It also formed as an early to middle-stage vein mineral, as an early to late-stage component of disseminated deposits, in both intrusive and hydrothermal breccias, and in altered rocks associated with disseminated deposits. It replaces clay and carbonates in supergene deposits formed by descent of sulfate-bearing water (Loughlin and Koschmann, 1935; Thompson et al., 1985; Thompson, 1992).
Hessite Ag^sub 2^Te (OV)
Hessite occurs as an early-stage mineral in microscopic, interstitial grains in calaverite in the Portland mine, where rich pyritic ore was shattered and recemented by tellurides, quartz and fluorite (Loughlin and Koschmann, 1935; Eckel, 1997).
Hornblende (undivided) (RA)
Hornblende is a rock-forming mineral that occurs as an inconspicuous component of phonolite. It also occurs in tephriphonolite dikes and stocks, in plagioclase phonolite, and in vogesite (Lindgren and Ransome, 1906; Loughlin and Koschmann, 1935; Thompson et al., 1985).
Hübnerite MnWO^sub 4^ (OV)
Lindgren and Ransome (1906) reported an occurrence of hübnerite in the Puzzle vein, where it formed radial, dark brown to dark green aggregates of striated prisms in a small vein associated with sphalerite and galena and intergrown with quartz. The Carbonate Hill breccia pipe also contains minor amounts of hübnerite, which in extremely rare cases has been observed coated with native gold.
Hyalophane (K,Ba)Al(Si,Al)^sub 3^O^sub 8^ (RA)
Hyalophane occurs as oscillatory zoned phenocrysts and rims on sanidine and anorthoclase phenocrysts in plagioclase phonolite (Birmingham, 1987).
Ilsemannite (?) Mo^sub 3^O^sub 8^.nH^sub 2^O (SO)
Ilsemannite was reported as dark blue, mammillary, water-soluble crusts associated with comb quartz, molybdenite, sphalerite, galena and ferrous sulfate; it formed by oxidation of molybdenite in a vein in the Ophelia tunnel (Eckel, 1997).
Jarosite K^sub 2^Fe^sub 6^(SO^sub 4^)^sub 4^(OH)^sub 12^ (SO)
Jarosite occurs as orange-brown, shiny crystals filling small quartz druses and as pseudomorphs after cubic pyrite crystals in oxidized breccia, sometimes associated with white barite. It also formed by alteration of early stage vein minerals and other alteration products by oxygenated water at the Gold Hill mine (Hildebrand and Gott, 1974; Thompson et al., 1985).
Kaersutite NaCa^sub 2^(Mg,Fe)^sub 4^Ti(Si^sub 6^Al^sub 2^)O^sub 22^(OH)^sub 2^ (RA)
Kaersutite occurs as reddish-brown, 1 to 2-mm crystals in the groundmass of plagioclase phonolite, tephriphonolite, and, rarely, vogesite (Birmingham, 1987).
Kaolinite Al^sub 2^Si^sub 2^O^sub 5^(OH)^sub 4^ (AH; SO)
Kaolinite forms by weathering and alteration of feldspars in Proterozic rocks and by hydrothermal alteration in the hydrothermal breccias and volcanics (Lindgren and Ransome, 1906; Thompson, 1992).
Krennerite (Au,Ag)Te^sub 2^ (OV)
Krennerite occurs in the vein deposits as small, vertically striated silver-white to pale brass-yellow prisms that commonly have been misidentified as sylvanite or calaverite. It may be intimately intergrown with calaverite (in parallel growth) and embedded in celestine or a "kaolin-like" material on pyritic quartz gangue (Lindgren and Ransome, 1906; Chester, 1898; Loughlin and Koschmann, 1935; Eckel, 1997).
Låvenite (?) (Na,Ca)^sub 2^(Mn,Fe)(Zr,Ti)Si^sub 2^O^sub 7^(O,OH,F)^sub 2^ (RA)
Låvenite has been reported as an accessory constituent of phonolite "near Cripple Creek," as minute, colorless or pale yellow needles either isolated or as groups of loose crystals. It was not found in the extensive work by Birmingham (1987) (Eckel, 1997).
Magnesiochromite MgCr^sub 2^O^sub 4^ (RA)
Birmingham (1987) reported the occurrence of magnesiochromite as dark brown inclusions in olivine in monchiquite, phonotephrite and tephriphonolite.
Magnetite Fe^sup 2+^Fe^sup 3+^^sub 2^O^sub 4^ (AH; RA)
Magnetite is an accessory mineral in lamprophyre, tephriphonolite, phonolite and plagioclase phonolite and in Proterozoic gneiss and granite. It also occurs as a minor component of wall-rock alteration of mafic rocks, and replacing biotite in the outer zone of alteration associated with vein deposits (Lindgren and Ransome, 1906; Thompson et al., 1985; Thompson, 1992).
Mallardite MnSO^sub 4^.7H^sub 2^O (SO)
Mallardite was reported as efflorescences in the Moon Anchor mine (Lindgren and Ransome, 1906).
Manjiroite (Na,K)(Mn^sup 4+^,Mn^sup 2+^)^sub 8^O^sub 16^.nH^sub 2^O (SO)
Manjiroite formed by weathering by oxygenated water at the Globe Hill mine (Thompson, et al., 1985).
Marcasite FeS^sub 2^ (GV; GD; SS)
Marcasite was an early-stage component of vein and diatremehosted deposits such as the Cresson and Ajax deposits. It was doubtfully identified as crusts in dolomite at Stratton's Independence mine. It also occurs as a supergene mineral formed by reduction of dissolved iron sulfates (Lindgren and Ransome, 1906; Loughlin and Koschmann, 1935; Thompson et al., 1985; Saunders, 1988; Thompson, 1992; Eckel, 1997).
Melilite (Ca,Na)^sub 2^(Al,Mg)(Si,Al)^sub 2^O^sub 7^ (RA)
Melilite was reported from a "basalt" (lamprophyre) dike by Loughlin and Koschmann (1935).
Melonite NiTe^sub 2^ (OV)
Melonite was found on the 2100, 2200 and 2300 levels of the Cresson mine, where it occurred as probable pseudomorphs after calaverite. The melonite forms oriented overgrowths on calaverite, which is partly replaced by melonite and native gold (Saunders, 1988; Eckel, 1997).
Mercury Hg (OV)
Native mercury has been reported in small amounts associated with cinnabar and coloradoite at the Moon Anchor mine (Lindgren and Ransome, 1906; Eckel, 1997).
Mirabilite Na^sub 2^SO^sub 4^.10H^sub 2^O (SO)
Mirabilite was reported as delicate efflorescences in old drifts in the oxidized zone in the Anaconda-Raven tunnel and the Last Dollar mine (Lindgren and Ransome, 1906).
Molybdenite MoS^sub 2^ (OV)
Molybdenite was common in vein deposits, where it formed soft, lead-gray scales and small masses, often intergrown with pyrite and sphalerite, at all depths below the oxidized zone (Lindgren and Ransome, 1906).
Montmorillonite (Na,Ca)^sub 0.3^(Al,Mg)^sub 2^Si^sub 4^O^sub 10^(OH)^sub 2^.nH^sub 2^O (AH; AD; AV)
Montmorillonite is a common hydrothermal alteration mineral, replacing plagioclase in wall rocks associated with veins and in both the matrix and fragments in hydrothermal breccias (Thompson et al., 1985; Thompson, 1992).
Muscovite KAl^sub 2^(Si^sub 3^Al)O^sub 10^(OH,F)^sub 2^ (RA; AH)
Muscovite occurs as a primary component of the Cripple Creek "granite" and Proterozoic schist. It is common as an alteration product ("sericite"), replacing nepheline in phonolite and replacing plagioclase and biotite in various volcanic rocks and breccias of the district (Lindgren and Ransome, 1906; Loughlin and Koschmann, 1935; Thompson et al., 1985; Thompson, 1992).
Nagyagite Pb^sub 5^Au(Sb,Bi)Te^sub 2^S^sub 6^ (OV)
Nagyagite coated by altaite is reported to form zones around sylvanite crystals (Stumpfl, 1970, Eckel, 1997).
Natrolite Na^sub 2^Al^sub 2^Si^sub 3^O^sub 10^.2H^sub 2^O (AH)
Natrolite was reported as an occasional constituent of altered phonolitic rocks (Lindgren and Ransome, 1906).
Nepheline (Na,K)AlSiO^sub 4^ (RA)
Nepheline is abundant as hexagonal prisms from microscopic size to 2 mm, some red, many partly altered to stilbite and other zeolites, and sometimes enclosed in analcime in phonolite (Lindgren and Ransome, 1906; Loughlin and Koschmann, 1935; Eckel, 1997).
Nontronite Na^sub 0.3^Fe^sub 2^(Si,Al)^sub 4^O^sub 10^(OH)^sub 2^.nH^sub 2^O (SO)
Nontronite occurs as soft, light yellow to greenish aggregates formed, in part, from iron derived from oxidation of pyrite near the surface and redeposited below. It has been reported from the Ida May and El Paso mines (Lindgren and Ransome, 1906; Loughlin and Koschmann, 1935; Lane, 1976; Eckel, 1997).
Nosean Na^sub 8^Al^sub 6^Si^sub 6^O^sub 24^(SO^sub 4^).H^sub 2^O (RA)
Nosean is a common constituent of rocks of the district, including phonolite, plagioclase phonolite, and tephriphonolite. One of the first minerals to form, it occurs as well formed, pale blue to green, 0.1 to 2-mm, dodecahedral crystals with inclusions arranged in two or more series, more abundant near the peripheries of the crystals (Lindgren and Ransome, 1906; Loughlin and Koschmann, 1935; Eckel, 1997).
Opal SiO^sub 2^.nH^sub 2^O (GV)
In the Zenobia mine, opal was locally an abundant last-phase primary vein mineral reported in vugs to great depth, as yellow masses of tangled wires and rods and as hyalite (Lindgren and Ransome, 1906).
Orthoclase KAlSi^sub 3^O^sub 8^ (RE; GV; GD; AH)
Orthoclase occurs with microcline in Proterozoic rocks of the district, as phenocrysts in plagioclase phonolite, as a major constituent of tephriphonolite and vogesite, as a part of the groundmass in monchiquite and as transparent to translucent crystals ("adularia") in both the veins and the inner and outer parts of altered host rocks (replacing biotite and microcline) of vein and diatreme-hosted deposits. "Adularia" was one of the first minerals deposited by hydrothermal activity in the district, sometimes occurring as dense masses intergrown with quartz (Lindgren and Ransome, 1906; Loughlin and Koschmann, 1935; Thompson et al., 1985; Eckel, 1997).
Pargasite NaCa^sub 2^(Mg,Fe)^sub 4^Al(Si^sub 6^Al^sub 2^)O^sub 22^(OH)^sub 2^ (RA)
Pargasite is very common as brown to olive-green microphenocrysts in vogesite, as tan megacrysts in monchiquite, and in tephriphonolite and plagioclase phonolite (Birmingham, 1987).
Pentahydrite MgSO^sub 4^.5H^sub 2^O (SO)
Pentahydrite was reported with epsomite in one analysis and with alunogen in another (Hobbs, 1905; Palache et al., 1951; Eckel, 1997).
Petzite Ag^sub 3^AuTe^sub 2^ (OV)
Petzite is uncommon at Cripple Creek. It has been reported from the Gold King mine and, in small amounts, elsewhere in the district (Lindgren and Ransome, 1906; Geller, 1993).
Phlogopite KMg^sub 3^Si^sub 3^AlO^sub 10^(F,OH)^sub 2^ (RA)
Phlogopite occurs as phenocrysts and as a constituent of the groundmass in vogesite and monchiquite (Birmingham, 1987; Thompson, 1992).
Plagioclase (undivided) (RE)
Plagioclase ranging in composition from albite to oligoclase occurs in plagioclase phonolite, phonotephrite, and tephriphonolite and in Proterozoic rocks. In vogesite its composition ranges from andesine to bytownite, and minor albite occurs in the groundmass of monchiquite (Lindgren and Ransome, 1906; Loughlin and Koschmann, 1935; Thompson, 1992).
Planerite (?) Al^sub 6^(PO^sub 4^)^sub 2^(PO^sub 3^OH)^sub 2^(OH)^sub 8^.4H^sub 2^O (SO)
Pale blue 5 mm to 1 cm-thick veinlets in altered granitic rocks are probably planerite (C. E. Raines collection, reported in Eckel, 1997).
Psilomelane; Wad (mixed Mn oxides) (SO)
Both hard, massive and soft, "sooty" unidentified manganese oxides were common as stains and fracture fillings, sometimes as irregular masses or nodules, in the Pharmacist and Summit mines (Lindgren and Ransome, 1906).
Pyrite FeS^sub 2^ (GV; GD; SS; AH)
Pyrite is the most common sulfide in the district, forming in most stages of vein formation and alteration. Pyrite occurs as subhedral cubic or pyritohedral crystals rarely larger than 1.5 cm, as masses and, rarely, as reniform coatings of radial, fibrous crystals on quartz. It occurs in veins (with most other vein minerals), in disseminated deposits (intergrown with native gold), and in altered rocks associated with both. In some cases it replaces original dark-colored mineral fragments (Lindgren and Ransome, 1906; Loughlin and Koschmann, 1935; Thompson et al., 1985; Thompson, 1992).
Pyroxene Group (undivided) (RA; RE)
Pyroxene, commonly not specifically identified, is an important constituent of many of the rocks of the district. Aegirine and aegirine-augite occur as phenocrysts and groundmass in plagioclase phonolite and tephriphonolite; augite in phonotephrite, monchiquite, and vogesite; and aegirine, aegirine-augite, and salite as acicular bundles to blunt crystals, some wrapping around nepheline or included in analcime, in phonolite (Lindgren and Ransome, 1906; Loughlin and Koschmann, 1935; Thompson et al., 1985; Birmingham, 1987).
Pyrrhotite Fe^sub 1-x^S (GV; GD)
Pyrrhotite occurs as an early-stage mineral of veins and hydrothermal breccias and as a late-stage mineral in the matrix of hydrothermal breccias (Thompson et al., 1985).
Quartz SiO^sub 2^ (RE; GV; GD; AH; AV)
Quartz is a major constituent of the Proterozoic granites, gneisses, and schists, a component of sediments buried in the basin, a principal vein mineral, and a component of hydrothermal breccias, intrusive breccias, and altered rocks associated with hydrothermal activity. In the veins, it occurs as crusts, combs, and granular masses, as colorless to somewhat smoky druses, as replacements of celestine, dolomite and calcite, as coatings concealing the tellurides and as late-stage yellow druses and droplets of chalcedony that coat earlier quartz and most other vein minerals. It frequently occurs intergrown with calaverite. Excellent amethyst crystals, in doubly terminated groups to 12.5 cm and clusters up to 15 cm across, were reported from the district as early as 1901 and can be found in many museum collections. However, the exact mine in which they were found remains unknown. The amethyst crystals are characterized by transparent, pale purple rhombohedron faces, some with purple phantoms, and elongated gray to pale lavendar striated prism faces. Divergent groups are typical. In the Bluebird mine, drusy quartz casts of large orthorhombic crystals (possibly barite) have been reported (Lindgren and Ransome, 1906; Loughlin and Koschmann, 1935; Thompson, 1992; Eckel, 1997).
Rhodochrosite MnCO^sub 3^ (GV)
Rhodochrosite is relatively rare, as pink rhombic crystals with fluorite, pyrite, galena and sphalerite in veins at the Moon Anchor, Fluorine, and Pointer mines (Lindgren and Ransome, 1906). In 2001, it was found in small amounts at the Cresson open-pit mine as bright, pinkish orange botryoidal crusts coated by celestine, creedite and gearksutite.
Roscoelite K(V,Al,Mg)^sub 2^(AlSi^sub 3^)O^sub 10^(OH)^sub 2^ (GV; AH)
Roscoelite occurs mostly as a product of wall-rock alteration, replacing plagioclase and biotite in the inner alteration zone of veins (e.g. Ajax mine). It occurs as small, soft, drusy masses or green colorings on the edges of veins or in inclusions. At the Mary McKinney mine, massive roscoelite occurred with quartz, fluorite and calaverite. Roscoelite and celestine were considered to be good ore indicators at the Cresson mine (Loughlin, 1927; Loughlin and Koschmann, 1935; Thompson et al., 1985; Thompson, 1992; Eckel, 1997).
Rutile TiO^sub 2^ (GV; RA; AH)
Rutile occurs as a middle to late-stage vein mineral, a minor accessory in the Cripple Creek "granite," and as microcrystals formed by alteration of titanite in plagioclase phonolite (Lindgren and Ransome, 1906; Thompson et al., 1985; Thompson, 1992).
Sanidine (K,Na)AlSi^sub 3^O^sub 8^ (RE)
Sanidine is a major constituent of various volcanic units, occurring as phenocrysts in phonolite and tephriphonolite (Birmingham, 1987; Thompson, 1992).
Serpentine (undivided) (AH)
Serpentine is a product of wall-rock alteration replacing olivine in mafic rocks of the district (e.g. monchiquite) and in altered plagioclase phonolite (Lindgren and Ransome, 1906; Thompson, 1992).
Sillimanite Al^sub 2^SiO^sub 5^ (RA)
Sillimanite is abundant in Proterozoic gneiss near Cameron and in schist (Lindgren and Ransome, 1906).
Sodalite Na^sub 8^Al^sub 6^Si^sub 6^O^sub 24^Cl^sub 2^ (RE or RA)
Sodalite is common as small (0.001 to 2-mm) dodecahedral crystals with transparent borders and dull brown interiors in phonolite, plagioclase phonolite and tephriphonolite (Lindgren and Ransome, 1906; Loughlin and Koschmann, 1935; Eckel, 1997).
Sonoraite FeTeO^sub 3^(OH).H^sub 2^O (SO)
Sonoraite is very rare as platy, vitreous, yellow-green crystals less than 1 mm in size, with native gold on gossan at the Hoosier mine (Eckel, 1997).
Sphalerite (Zn,Fe)S (OV; OD)
The second commonest sulfide at Cripple Creek, sphalerite occurred in veins as small reddish brown masses intergrown with pyrite, galena and fluorite at all depths below the oxidized zone.
It was an early-stage mineral in the veins and early to middle-stage in disseminated deposits and breccias (Lindgren and Ransome, 1906; Loughlin and Koschmann, 1935; Thompson et al., 1985).
Stibiconite SbSb^sub 2^O^sub 6^(OH) (SO)
Stibiconite occurred as a yellow-brown alteration product of stibnite from the Independence mine (Eckel, 1997).
Stibnite Sb^sub 2^S^sub 3^ (OV)
Although uncommon in collections, stibnite was locally abundant as bunches of striated crystals weighing up to 50 pounds (at the C.K. & N. mine); this stibnite is frequently rich in gold because of admixed calaverite. Stibnite also occurs with "gray copper" (tetrahedrite), chalcedony and fluorite. Locally, quartz coated stibnite that subsequently dissolved, leaving hollow quartz casts called "splinters." Stibnite alters to stibiconite (Bancroft, 1903; Lindgren and Ransome, 1906; Saunders, 1988).
Stilbite NaCa^sub 2^Al^sub 5^Si^sub 13^O^sub 36^.14H^sub 2^O (AH)
Stilbite is reported as an alteration product of analcime (Lindgren and Ransome, 1906) or nepheline (Eckel, 1997) in vogesite dikes.
Strengite FePO^sub 4^.2H^sub 2^O (SO)
Strengite was reported from the John A. Logan mine, where it occurred in two generations in thin limonitic fractures in a gray, partly oxidized orthoclase-quartz-pyrite rock. The first generation consists of spherules of radiating white to colorless concentrically zoned crystals. The second occurs as crusts and spherules of shiny gray crystals to 0.03 mm. Strengite is associated with cacoxenite and a member of the rockbridgeite family (Eckel, 1997).
Sylvanite (Au,Ag)^sub 2^Te^sub 4^ (OV)
Sylvanite is a middle-stage mineral of vein deposits, occurring with calaverite and krennerite. It is found as brilliant, steel gray to silver-white (sometimes yellowish) simple prismatic or bladed crystals, contact twins and penetration twins that result in arborescent or reticulated aggregates on fracture surfaces. Some authors (Tunnell, 1954) report that most material identified as sylvanite is really krennerite, but other workers have found the opposite to be true (D. Bunk, personal communication). Reported from the Anchoria-Leland, Blue Bird, Elkton, Independence, Little May, Mabel M, Moon Anchor, Portland, and Victor mines, among others (Lindgren and Ransome, 1906; Loughlin and Koschmann, 1935; Tunnell, 1954).
Talc Mg^sub 3^Si^sub 4^O^sub 10^(OH)^sub 2^ (AH)
Talc is a minor product of wall-rock alteration of mafic rocks (presumably olivine). It is also reported from the Lady Stith claim, associated with kaolinite, gypsum, fluorite, and tyuyamunite (Nelson-Moore et al., 1978; Thompson, 1992).
Tellurite TeO^sub 2^ (SO)
Tellurite occurs as slender, transparent soft white or yellowish white, prismatic to tabular crystals to 2 mm, many with vicinal faces, and as small spherical masses in the oxidized zone of the WPH, Gold Sovereign and Blue Bird mines. Occurs with emmonsite and native gold (Lindgren and Ransome, 1906; Eckel, 1997).
Tellurium Te (OV)
Native tellurium has been reported in crystals from vein deposits on Raven Hill (Lindgren and Ransome, 1906).
Tennantite (Cu,Ag-Fe,Zn)^sub 12^As^sub 4^S^sub 13^ (OV)
Tennantite occurred with tetrahedrite in vein deposits of the El Paso mine (Lane, 1976).
Tetrahedrite (Cu,Fe,Ag,Zn)^sub 12^Sb^sub 4^S^sub 13^ (OV)
Tetrahedrite is a locally conspicuous and very widespread early-stage vein mineral at Cripple Creek; dark steel-gray masses may also result from secondary sulfide enrichment. Tetrahedral crystals occurred at the Abe Lincoln and Doctor Jack-Pot mines. It always contains silver; the richest silver ore in the district is tetrahedrite-rich. Overgrowths show concentric zones successively enriched with zinc, silver and antimony (Lindgren and Ransome, 1906; Loughlin and Koschmann, 1935; Geller, 1993).
Thalenite-(Y) Y^sub 3^Si^sub 3^O^sub 10^(F,OH) (RA)
Birmingham (1987) reported uncommon thalenite-(Y) as very minute crystals in the groundmass of phonolite.
Titanite CaTiSiO^sub 5^ (RA)
Titanite occurs as small yellow crystals in plagioclase phonolite and as a minor accessory in phonolite, tephriphonolite, and Proterozoic rocks (Lindgren and Ransome, 1906; Loughlin and Koschmann, 1935; Thompson et al., 1985).
Topaz Al^sub 2^SiO^sub 4^(F,OH)^sub 2^ (RA)
Birmingham (1987) reported an occurrence of topaz in syenitic fragments in hydrothermal breccia from Globe Hill (Thompson et al., 1985; T. B. Thompson, personal communication, 2003).
Torbernite/Metatorbernite Cu(UO^sub 2^)^sub 2^(PO^sub 4^)^sub 2^.8H^sub 2^O (SO)
Torbernite occurred with autunite in an altered Tertiary plug on Rhyolite Mountain (Nelson-Moore et al., 1978; Eckel, 1997).
Tourmaline Group (undivided) (RA)
Tourmaline is a minor accessory in Proterozoic rocks of the district (Lindgren and Ransome, 1906).
Turquoise CuAl^sub 6^(PO^sub 4^)^sub 4^(OH)^sub 8^.4H2O (SO)
Turquoise has been found at scattered occurrences in the district, including Mt. Pisgah. On the south flank of Mineral Hill, two small cuts are now being intermittently worked for turquoise by Wally Burtis (Florence claim) and the Bad Boys of Cripple Creek Mining Company (Elkhorn claim, higher upslope), respectively. Both operations typically mine thin, irregular veinlets of turquoise, to 1 cm wide, which cut altered Precambrian granite (P. Modreski, 2004, personal communication). Specimens up to six pounds are known (Murphy and Modreski, 2002).
Rare visible gold intergrown with limonite has been reported to occur within the turquoise from the Elkhorn claim (Murphy and Modreski, 2002).
After a heavy rain, small chips and fragments of turquoise can be found in the streets of Cripple Creek; this turquoise is believed to have originated from Mineral Hill, some of whose old dumps were used as gravel road fill (P. Modreski, 2004, personal communication). Turquoise pseudomorphs after prismatic quartz or apatite crystals have been found at the O'Haver claim. Elsewhere, specimens of excellent color, containing pyrite inclusions, are reported (Eckel, 1997).
Tyuyamunite/Metatyuyamunite Ca(UO^sub 2^)^sub 2^V^sub 2^O^sub 8^.3H^sub 2^O (SO)
Tyuyamunite was reported from a shear zone associated with Tertiary intrusives at the Lady Stith claim, just east of Cripple Creek, where it occurred with fluorite, talc, kaolin and gypsum (Nelson-Moore et al., 1978; Eckel, 1997).
Wavellite Al^sub 3^(PO^sub 4^)^sub 2^(OH,F)^sub 3^.5H^sub 2^O (GV)
Small, white, spherical, radial masses of wavellite occurred at the Raven and Bertha B mines. It was also reported as yellow microcrystalline clusters and tufts of radiating acicular crystals at the Moon Anchor mine, and at the May mine and elsewhere (Lindgren and Ransome, 1906; Eckel, 1997).
Zinkenite Pb^sub 9^Sb^sub 22^S^sub 42^ (OV)
Zinkenite occurred as microscopic, long, slender, hexagonal prisms in cavities at the Ramona mine, associated with krennerite (Eckel, 1997).
Zircon ZrSiO^sub 4^ (RA; AH)
Zircon occurs as an accessory species in Proterozoic rocks of the district and in phonolite and plagioclase phonolite. It is locally abundant in the Pikes Peak Granite (Lindgren and Ransome, 1906).
Zirkelite (Ca,Th,Ce)Zr(Ti,Nb)^sub 2^O^sub 7^ (RA)
Birmingham (1987) reported sparse, microscopic crystals of zirkelite in phonotephrite and tephriphonolite on the surface at the Vindicator mine.
Special thanks to Dave Bunk who not only provided slides of some of his outstanding Cripple Creek specimens but also reviewed the first draft of the manuscript, providing much useful feedback.
Source: Mineralogical Record