September 4, 2008
Collecting Microminerals in the Creede Mining District
By Smith, Arthur E
The Amethyst, Commodore No. 5 & Bulldog Mountain Mines Mineral County, Colorado
The initial discovery of silver ore in the Creede district was at the Holy Moses mine high above East Willow Creek, but the district did not prosper until additional discoveries were made along West Willow Creek on the Amethyst vein system. The Amethyst and Commodore No. 5 mines are located on West Willow Creek approximately 1.5 miles north of Creede. The Commodore No. 5 ore bins are the first structures one encounters when traveling north up the canyon. The road rejoins the creek level near the Commodore No. 5 adit, and at this juncture one is afforded a spectacular view of the earlier adits of the Commodore mine perched on the mountainside. The Amethyst mine is north of the Commodore mine, and most of its production occurred during the 1890s and early 1900s, but despite periods of exploration after 1935, the mine has not had any sustained production. On the other hand, the Commodore mine, which also had pre-1900 production, had been in operation since 1934 by Emperius Mining Company. The mine continued to operate, with only brief idle periods, until 1972 when mining was suspended (Huston 2005). Minerals Engineering Company explored and mined the Commodore mine through 1976, followed by Houston Oil and Minerals and later by Chevron Oil Company, which continued operations into the 1980s. Emperius Mining also produced ore from the P and OH veins that are adjacent to the Amethyst vein system. The early-mined ore from the Amethyst vein was oxidized and enriched in silver; however, with deeper mining in later years, it turned to base-metal sulfide ores with some silver present. Emperius Mining attempted to establish silver reserves in the late 1960s and early 1970s from the enriched oxide zones by driving a raise 400 feet up into the Commodore 4 level. This evidently was unsuccessful because no significant mining ensued (Huston 2005). Sporadic exploration was carried on after the 1980s in the area, but at present no mining is taking place in the Creede mining district.
Collecting on the Commodore No. 5 and Amethyst Mine Dumps
My first trip to Creede was in 1966 while on a two-week vacation in Colorado. One of the first mine dumps I collected was the Commodore No. 5, which produced a number of small crystals of sphalerite, galena, and pyrite; however, at that time I had not become interested in microcrystals, so the material I found did not hold my interest.
By 1971 I was well into micromounting, and revisiting some of the mine dumps in the Creede area was in our vacation plans. That year I brought home several flats of material from the Commodore No. 5 and other mines and was rewarded with a number of fine microcrystals after reducing the collected material with a trimmer. In 1976 I had very good luck on the same Commodore No. 5 mine dump with the recovery of a pocket of native silver wires partially hidden by green chlorite (Smith 1995).
A visit in 1978 revealed that activity at the Commodore mine had slowed down, and the mine appeared to be on its last legs. Collecting that year was discouraging, and I realized I would do better by purchasing specimens from miners than by working the mine dumps (Smith 1994). A few more trips were made to the Creede area in the 1980s, again with disappointing results.
Minerals of the Amethyst and Commodore No. 5 Mines
The following are minerals I have collected or seen from the Amethyst and Commodore No. 5 mines. I have emphasized the microminerals that were collected and observed from the late 1960s to the early 1980s. It is not intended to be a complete mineralogy of the district for the West Willow Creek mines; for that, readers are referred to Emmons and Larson (1923), Raines (1988), and Eckel (1997).
Anglesite was not common and rarely formed prismatic, colorless, drusy crystals to 0.3 mm. It also occurred as a white coating on galena.
Acanthite was usually associated with native silver. Rarely, crude prismatic microcrystals were observed, but it was more common as tiny groups of minute, free-standing dendritic-like groups of shiny black, thin, elongated crystals.
Barite was collected at the Amethyst mine as groups of thin, tabular, white crystals with rounded corners associated with aggregates of minute, tan, rounded sphalerite crystals (confirmed by EDS). The barite crystals range to 5 mm across.
Cerussite was rare as colorless to pale yellow, somewhat rounded, bright, microscopic crystals. In 1981, I purchased a small-cabinet- sized specimen of stemlike, subparallel white cerussite crystals. Some of the crystals have a small hollow tube running down their centers. Individual crystals are 3-4 mm across and up to 1 cm long. On some of the stemlike crystals, white to colorless, minute, tabular crystals protrude from the sides.
Chalcopyrite was common as masses and crystals to 1 cm. Rarely, were they bright and shiny, with most having a dull gray, greenish- gray, or black patina. The sphenoidal crystals vary from unmodified to highly modified. Native silver and acanthite were occasionally found associated with chalcopyrite.
Chamosite was probably the correct name of the green aggregates of chlorite that, at the time, were called thuringite. Chamosite is prominent on some specimens collected in the 1970s from the Commodore No. 5 mine. It occurred on other minerals, and some completely filled cavities as loose green aggregates. Generally, the chamosite is in minute spheres that may rarely reach 0.5 mm across, particularly when the spheres are not in aggregates.
Covellite was observed as dark blue coatings on pyrite and chalcopyrite. One pyrite specimen coated with covellite has small aggregates of minute tan crystals on it that may be jarosite or plumbojarosite. Identification of these minerals has not been confirmed.
Cuprite, variety chalcotrichite, was found in the oxidized zone on gossan. It forms groups of red acicular crystals oriented in two different directions, forming a loose reticulated pattern.
Fluorite occurred as cubic and octahedral crystals modified by other forms. The octahedral faces may be composed of numerous minute stairstep cubes that give the face a rough appearance. Rarely, fluorite occurred as compact crystal aggregates to 5 mm in maximum dimension. The color varies from colorless to pale greenish-blue and pale purple.
Galena was the most important ore mineral and occurred as large, bright, cleavable masses and crystals. Crystals to 1 cm were not uncommon from the dumps, and some large crystals and crystal groups have been available for purchase. Most of the galena crystals are cubes, but some of the microcrystals show combinations of cube and octahedral faces. Some of the cubes are partially hoppered; others show overgrowths of tiny cubes on some faces. Many of the galena crystals I collected in the 1970s have a characteristic thin coating of reddish hematite. Some acicular crystals of galena to 1 cm long were collected from the dump in 1971. They appear to be formed by a series of elongated crystals attached to each other, end to end. Cubic crystals of galena under 3 mm cover what appear to be stalactitic growths to 5 cm long with a hollow tube down their center.
Gypsum was not common on the dumps. White to transparent, elongated crystals reach 1 cm long. It occurs as single crystals and as groups of crystals.
Hematite was common on specimens collected in the 1970s. It occurred as microscopic, dark red-brown, thin discoids on quartz and other minerals. It is also present as reddish greasy coatings on galena and quartz.
Hemimorphite was rare outside the oxidized zone and occurred as small, thin-bladed crystals in minute cavities and on other minerals.
Ktenasite was described as minute, blue-green, flattened prismatic crystals on chalcopyrite and sphalerite by Olsen and Lewis (1979). It was fairly common in the Commodore No. 5 dump in the 1970s.
Malachite that had been reported as a grayish-green to pale bluish-green surface alteration of chalcopyrite is probably ktenasite.
Marcasite was present in pyrite masses that were fairly common from the mines on West Willow Creek. Crystals were not observed, but the relatively rapid deterioration of some sulfide masses attests to its probable presence.
Orthoclase, variety adularia, was reported to form veinlets in rhyolite at the Amethyst mine.
Pyrite was common on the dumps in the 1970s as bright botryoids and masses several centimeters across, with some showing pyritohedral crystals to 6 mm.
Pyrolusite, often called manganite, occurred as fans of acicular crystals embedded in massive pyrite-marcasite. The crystals are blue- black and up to 2.5 cm long. Unfortunately, both the pyrolusite crystals and the matrix tend to be unstable, and most of the specimens I collected in the early 1970s have disintegrated.
Pyromorphite occurred as small, yellow and brown crystals in the upper portions of the Amethyst vein (Eckel 1997). Quartz was abundant as small crystals at both the Amethyst and Commodore mines. Most were colorless, white, or amethystine and ranged to 4 cm in length. Some of the small crystals from the Commodore No. 5 mine have had their prism faces partly dissolved by later solutions, causing them to form crude scepters. The Amethyst mine is noted for pale blue, banded agate called "sowbelly agate" (because the long pieces look like slabs of bacon). Specimens of this agate showed bands to 6 cm wide and reached a length of 20 cm.
Rhodochrosite was uncommon in the Commodore No. 5 mine, but tiny aggregates of 2-mm pale pink rhombohedra were collected with quartz crystals and other minerals on the dump. Some of the rhombohedra are distorted into discoids.
Siderite, or possibly iron-rich rhodochrosite, occurred as pale tan rhombs. Darker rhombs to 4 mm across occurred as tightly packed crystal groups, but when found on the mine dump, they had turned a darker color from exposure.
Silver was not common on the mine dumps in the 1970s, but some isolated pockets were discovered with both small wires and tiny arborescent crystal masses. Most of the silver specimens purchased from miners and rock shops at that time were probably from the Bulldog Mountain mine, which was also in operation.
Sphalerite was the most abundant crystallized ore mineral present in specimens collected during the 1970s. Crystals range to 4 cm across, but the most gemmy, well-formed, and colorful are commonly under 1 cm. Their color varies from shades of green, yellow, amber, and brown to jet-black. The smaller crystals show a variety of simple to complex crystal forms and are often twinned.
Stephanite was collected as compact groups of shiny black, prismatic crystals in small cavities in quartz. The crystals were typically less than 0.3 mm in size. Dendritic black acanthite may occur on the same specimen but is not directly associated with the stephanite.
Tetrahedrite was rare, and I collected only a single microscopic black mass showing tetrahedral faces in the early 1970s.
Bulldog Mountain Mine
The Bulldog Mountain mine is located about a mile northwest of Creede on Bulldog Mountain. Early shallow shafts and adits failed to find ore, but after the release of a preliminary study by the U.S. Geological Survey in 1960 (Steven and Ratte 1965), interest in the area was renewed. Steven and Ratte proposed the likely possibility that the Bulldog Mountain Fault Zone was mineralized, and in 1963 Homestake Mining Company began exploration. The soft nature of the vein and numerous vugs made diamond drill core recovery poor and unreliable. In 1964 Homestake made the decision to drive a drift on the vein at an elevation of 9,700 feet, and eventually high-grade silver ore was intersected along the vein. A milling facility was constructed in 1968, and mining began on the Puzzle vein in 1969 and continued until 1985 when mining operations were suspended. During the life of the mine, 25 million ounces of silver and 48 million pounds of lead were produced. The following description of what the miners encountered underground was given by A. Bopper in Huston (2005).
While driving the tunnel on the 9,700-foot level, the miners intercepted some of the most beautiful native silver ever discovered in the Creede mines. There was wire silver that looked like steel wool, massive leaf silver over an inch wide, and large amounts of ruby silver (pyrargyrite). When the miners went into the mine and saw what the previous shift had blasted into, they could not believe their eyes. It was likened to a pirate's treasure chest, only much larger! This high-grade ore pocket was mined upwards a distance of 240 feet from the 9,700-foot level.
The host rock for the silver-rich Puzzle vein is the Campbell Mountain Member of the Bachelor Mountain Rhyolite, which consists of an ash-flow tuff. The vein became non-productive in the shallower, softer portion of the Campbell Mountain Rhyolite; this is the main reason the ore was not discovered earlier (Jackson 1974). Evidently, the same was true in the West Strand vein, which was the original exploration target but was mined later than the Puzzle vein. The Puzzle vein, which was formed by fissure filling of faults, is an epithermal precious-metal vein composed of layered barite, galena, sphalerite, silver, and silver sulfosalts. The upper portion of the vein shows oxidation and supergene enrichment. This is in strong contrast to the base-metal deposition of the adjacent P, OH, and Amethyst veins that were mined in the Commodore and Amethyst mines (Plumlee 1994).
Collecting Minerals from the Bulldog Mountain Mine
My first acquaintance with Bulldog Mountain mine minerals was in 1966 in a mineral shop located on the main street of Creede. The shop was owned by "Pug" Sutherland, and as I remember, his prices were a little steep for my pocketbook, and the quality of the specimens was not great. He had barite, silver, and acanthite specimens, but none were attractive enough to tempt me to make a purchase.
In 1971 I was back in Creede with a mutual acquaintance and met someone who worked in the mine. He gave us specimens of native silver, pyrargyrite, acanthite, and amethyst. We were so overwhelmed with his generosity that we ignored the great specimen sitting on top of the television that probably could have been purchased for $50 (Smith 1995).
Another excellent source of minerals from the mine was Al Birdsey, a former miner. I bought specimens from him between 1971 and 1978, many of which were rich silver ore. Homestake Mining was aware of his business dealings, and he showed me two letters from the company telling him to "cease and desist" selling specimens that had been highgraded from the mine. He never let me see or offered his best silver specimens, saying they were saved for another collector. Actually, at the time, I was more interested in microscopic specimens, so it did not matter. On one trip he showed me a half-gallon jug full of small groups of arborescent copper specimens from a clay seam. They had been collected in the oxidized zone of the vein. Eventually, I managed to purchase the entire lot that was left in the jug. (Birdsey would rather sit down and talk a bit than sell specimens, so it was always an interesting visit as well as a challenge to coax him to show specimens that were not set out. Talking seemed to jog his memory of treasures that he had stashed away.)
Minerals of the Bulldog Mountain Mine
The following are descriptions of minerals, mostly microscopic, that I have seen, been given, bought, or collected at the Bulldog Mountain mine, with a mention of some occurrences from the literature. For more complete descriptions of some of the minerals at the mine see Raines (1988), Plumlee and Whitehouse-Veaux (1995), and Eckel (1977).
Acanthite is now recognized as a paramorph after argentite because it is not stable after formation. It is particularly common as dusty black coatings on white barite or quartz. It commonly occurred as irregular crystals that, when intergrown, form small masses. Rarely, it is seen as tiny, cubic, black crystals and as highly modified crystals. Acanthite may be associated with wire silver that often appears to have grown from it. Skeletal crystals are of two types: most are incompletely formed crystals; others appear to have been etched or partly reabsorbed. Elongated crystals to 2 mm are common. Delicate arborescent groups of thin, shiny black crystals similar to those from the Commodore mine are larger and more common at the Bulldog Mountain mine; a few resemble a small bird's feathers. Arborescent crystals are the last acanthite to form and may partially coat wire silver or large cubic acanthite crystals, giving them a hairy appearance. Most groups are small, less than 1 mm, but rarely patches of crystals may reach 5 mm across.
Barite was the most dominant gangue mineral in the Puzzle vein. It generally was white and occurred as masses-large plates with thick to very thin tabular crystals to 10 cm across. Barite is often associated with native silver, dusted with sooty-black acanthite microcrystals and with crystalline masses and crystals of other sulfides.
Bornite was observed as iridescent masses in quartz on a specimen that had stibnite crystals in small pockets. It also occurred with galena and acanthite.
Cerussite replaced galena in the upper portions of the ore zone (Plumlee and Whitehouse-Veaux 1994). It occurred as small, white or colorless crystals to 2 mm in length. I found one small specimen with minute crystals while examining ore samples.
Chalcopyrite was not as conspicuous in the Bulldog Mountain mine ores as elsewhere, but it was observed as sphenoidal microcrystals and small masses. Much of the chalcopyrite is covered by pyrite and is difficult to recognize unless in distinct crystals or broken portions.
Chlorite was reported by Plumlee and Whitehouse-Veaux (1994) as thin, pale gray coatings on some minerals. Thin white coatings on many of the arborescent copper crystal groups are thought to be chamosite, a chlorite-group mineral.
Copper occurred as small arborescent crystal groups in a clay seam in the oxidized portion of the vein. These groups are up to 1 cm across and show a flattened, elongated habit; some appear to be spinel-law twins. Copper was also reported as curved wires and as being associated with cuprite, variety chalcotrichite (Eckel 1997).
Cuprite, variety chalcotrichite, occurred with native copper and as small nests of red acicular crystals (Eckel 1997) that were restricted to the oxidized ore zones.
Digenite occurred in veinlets with tetrahedrite, galena, and other sulfides (Plumlee and Whitehouse-Veaux 1994).
Fluorite was inconspicuous but was reported from the Bulldog Mountain mine as pale yellow-green to green, cubic crystals and irregular masses. Cubic molds formed by the removal of fluorite have been observed (Plumlee and Whitehouse-Veaux 1994). Galena, though inconspicuous in much of the ore, did occur as outstanding cubic crystals to more than 4 cm on edge. These crystals are smooth, skeletal, or partly intergrown with each other. Many microscopic crystals have thin coatings of pyrite, chlorite, and clay minerals that make them difficult to distinguish from cubic acanthite. However, many of the galena cubes are more modified than acanthite and are a dull pale gray in contrast to the acanthite and sulfosalts that are generally black.
Gypsum probably formed as a postmining coating from the oxidation of pyrite. It occurred as colorless, clear, elongated crystals that sometimes spanned small cavities. It was also observed as typical flat monoclinic crystals in seams. All of the crystals observed were less than 2 mm in maximum dimension.
Halloysite was the white clay mineral that occurred in the oxidized portion of the vein (Plumlee and Whitehouse- Veaux 1994).
Hematite was reported (Plumlee and Whitehouse-Veaux 1994) but was inconspicuous in samples that I examined. Illite was reported in green pods (Plumlee and Whitehouse- Veaux 1994).
Jarosite was assumed to be the secondary yellow mineral that occurred as small, opaque, smooth but dull spheres and hemispheres and larger, more irregular bright spheres to 0.6 mm in diameter that appear to be composed of minute platy crystals. Jarosite also formed yellow coatings on other minerals, particularly pyrite and other sulfides in ore specimens.
Mimetite occurred as white to almost colorless crystals to 2 mm long, sometimes associated with pyromorphite crystals in oxidized portions of the Puzzle vein (Eckel 1997).
Orthoclase, variety adularia, occurred as crystals to 0.5 mm in size (Plumlee and Whitehouse-Veaux 1994).
Polybasite-pearcite was common in some portions of the orebody. Thin, crude, hexagonal prismatic crystals to 2 mm across were common. Rarely, compact aggregates of the crystals form what appear to be prismatic crystals that have a hexagonal outline. Some of the flat faces of the crystals are smooth, but most are grooved. Some of the grooves are parallel; others form complete trigonal patterns. Generally, crystals are black, but some have a bluish iridescence. Compact masses of intergrown crystals are common, with some appearing to have formed in cavities of other minerals or to have replaced them. The cavities are preserved by partial coatings of pyrite.
Pyrargyrite-proustite occurred in quartz and barite as small masses of tiny individual crystals. They are typically black or dark gray and rarely exhibit a reddish overtone. Larger crystals, seldom over 1 cm, were observed (Plumlee and Whitehouse-Veaux 1994). Microscopic compact bundles of elongated black crystals with a reddish cast to 2 mm long were observed intergrown on one end with crystalline masses of polybasite-pearcite and acanthite. Most of the crystals are irregular; some have a thin coating of pyrite and are not recognized until broken, thereby exposing the internal red color. Minute, bright red, prismatic crystals are possibly proustite and are extremely rare.
Pyrite was common in many areas of the mine as large botryoidal masses, concentric masses, fibrous masses, and sheets. It is abundant in most specimens, but well-formed crystals are uncommon. The sheets may have been part of epimorphs originally coating an unknown mineral. Microscopic cubic and pyritohedral crystals to 0.5 mm were present in the ore. Small "sunbursts" to 1 cm across with a radiating structure were observed.
Pyromorphite rarely occurred as minute, yellow, acicular crystals on and associated with mimetite.
Quartz occurred in white crystals up to several centimeters in length. It was common in the deposit but not always conspicuous in specimens. Drusy crystals lined small irregular cavities in some areas; in other places quartz may have formed epimorphs of unknown crystals no longer there. White to yellow chalcedony occurred as masses and coatings. Black chalcedony had included fine-grained sulfides (Plumlee and Whitehouse-Veaux 1994).
Rhodochrosite dominated the first stage of mineralization (Plumlee and Whitehouse-Veaux 1994) and occurred as finely to coarsely crystalline masses showing banding and, in some cases, brecciation. Crystals may be scalenohedral but more commonly are rhombohedral. The color varies from pale to dark pink and may also be buff, pale brown, or orange; however, the color variation does not accurately represent the composition, which may be up to 30 percent iron. Gemmy pink rhombohedral crystals range to 1 cm and are rare in most Colorado collections. My one short collecting stint on the dump in 1981 yielded massive pink rhodochrosite in specimens often weighing several pounds.
Silver had many forms: small arborescent crystal groups, loose masses of curly wires, ropes formed of composite subparallel wires, blebs, irregular masses, and thin bright spangles. Wires of silver that grew from corroded masses and crystals of acanthite are common, as are secondary arborescent crystals of acanthite that formed on composite silver wires.
Sphalerite was seen in crystalline fine-grained brown bands and crusts that were intergrown with galena. These coatings often form a base for later-formed sulfides and sulfosalts. Crystals are uncommon and are generally shades of green, although some reddish to brown crystals have been observed. Single crystals range to 2 cm, and many are twinned.
Stibnite occurred as 1-mm black, acicular crystals in drusy quartz crystal cavities. In the only specimen that I saw, bornite, galena, and chalcopyrite were present in the matrix but not directly in contact with the stibnite.
Tetrahedrite-tennantite was present in the ores of the Bulldog Mountain mine as black masses with acanthite and other sulfides. Crystals to 1 cm across have been reported (Eckel 1997). Fine- grained tetrahedrite may be disseminated or included in sphalerite (Plumlee and Whitehouse-Veaux 1994). I did not recognize any tetrahedrite-tenantite crystals in the material I examined, but there are many poorly formed and intermixed black sulfides and sulfosalts that make up the ore.
Wulfenite was extremely rare, with only a single yellowgray crystal reported with cerussite (Eckel 1997).
Xanthoconite-pyrostilpnite occurred as intergrowths with pyrargyrite-proustite (Plumlee and Whitehouse-Veaux 1994). Flat, elongated, dark crystals with pointed terminations occurred with pyrargyrite-proustite and may be either of these minerals; they have not been tested.
Famatinite, jalpaite, mckinstryite, and miargyrite are other silver-bearing minerals and were reported by Plumlee and Whithehouse- Veaux (1994). It is not known if they occurred in recognizable crystals or if they have just been identified in polished sections as microscopic intergrowths in chalcopyrite.
I thank John Frost of Houston, Texas, who graciously shared some of his Bulldog Mountain mine ore specimens and allowed me to break them down and greatly expand my knowledge of the microcrystals. Thanks are also extended to William Besse for preparing the map. Nancy Farah, Mark Jacobson, and Tom Rosemeyer read the article and offered helpful suggestions.
Eckel, E. B. 1997. The minerals of Colorado-Updated and revised. Denver, CO: Friends of Mineralogy, Colorado Chapter.
Emmons, W. H., and E. S. Larson Jr. 1923. Geology and ore deposits of the Creede district, Colorado. U.S. Geological Survey bulletin 718.
Huston, R. C. 2005. A silver camp called Creede: A century of mining. Montrose, CO: Western Reflections.
Jackson Jr., D. 1974. Homestake's hard work pays off at Bulldog Mountain mine. Engineering and Mining Journal 175 (5): 65-70.
Olsen, E., and C. F. Lewis. 1979. Ktenasite from Creede, Colorado. American Mineralogist 64:446-48.
Plumlee, G. S. 1994. Fluid chemistry evolution and mineral deposition in the main-stage Creede epithermal system. Economic Geology 89:1860-92.
Plumlee G. S., and P. H. Whitehouse-Veaux. 1994. Mineralogy, paragenesis, and mineral zoning of the Bulldog Mountain vein system, Creede, Colorado. Economic Geology 89:1883-1905.
Raines, E. 1988. Mineralogy of the Creede district, Mineral County, Colorado. In Mineralogy of precious metal deposits, 94-105. Colorado Chapter, Friends of Mineralogy and Department of Geology, Colorado School of Mines.
Smith Jr., A. E. 1974. Minerals of Creede, Mineral County, Colorado. Rocks & Minerals 49:394-99.
_____. 1994. Mineral stories: Good deal. Mineralogical Record 25:307.
_____. 1995. Mineral stories: Being kind to tourists. Mineralogical Record 26:505-6.
_____. 1995. Mineral stories: The best deals passed by. Mineralogical Record 26:567-68.
Steven, T. A., and J. C. Ratte. 1965. Geology and structural control of ore deposits in the Creede district, San Juan Mountains, Colorado. U.S. Geological Survey professional paper 487.
ARTHUR E. SMITH
9118 Concho Street
Houston, Texas 77036
Unless otherwise noted, all photos by the author of specimens from his collection
Arthur E. Smith, a consulting editor of Rocks & Minerals, is a retired geologist and a frequent contributor to publications in the Earth sciences.
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