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| The author stands at the entrance of the old Cuprite Mine in the Medicine Bow Mountains. |
After 30 years of exploring Wyoming for gold, diamonds, gemstones, other minerals and its fabulous geology, it was time to put together some geology guides to the region. This one is for Snowy Range within the Medicine Bow Mountains. These ancient mountains record more than 2.5 billion years of geologic history in a unique succession of outcrops, peaks, and ridges. Rock successions similar to those found in the core of the Medicine Bow Mountains are quite rare on the surface of the earth and are found only in a few other places in the world, such as the Witwatersrand Basin of South Africa.
The oldest rocks in the Medicine Bows are more than 2.5 billion years old. They are so old that they formed long before any complex lifeforms developed on the planet. In fact the oldest rocks crystallized long before the earth's atmosphere became sufficiently oxygen-rich to support any known type of life other than the simplest plankton and algae.
These and younger rocks exposed in the Medicine Bow Mountains record many interesting geological events, such as 2.5 to 1.7 billion-year-old rivers and streams eroding millions of tons of sediment from a highland to the north and carrying the sediment to a nearby ocean basin a relatively short distance to the south. South of the ancient coastline of this basin, about 2.0 to 1.8 billion years ago, island chains with active volcanoes erupted large volumes of ash and lava. Portions of the ancient sea floor were then subducted under the ancient continent forming a major suture (fault) between these two contrasting lands.
More recently in geologic history (about 100 million years ago), a major mountain building event known as the Laramide Orogeny began with the slow and periodic rise of the Medicine Bows above the nearby basins. Much later, during the Pleistocene (2 million to 10,000 years ago), glaciers carved shallow basins in the hard quartzite of the Snowy Range, leaving behind high alpine lakes in their wake.
When Mankind arrived, the Medicine Bow Mountains were not only explored and hunted by Indians, but also prospected by hundreds of prospectors searching for riches. In their sojourns, gold fever inflicted many, and they dug tunnels and searched stream gravels in the search of precious metals. Some found gold, but most left as broke as they came, although much richer in experience.
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| Geologic map showing Mullen Creek-Nash Fork shear zone (from Karlstrom and others, 1981). |
Although many of these mineral resources have lost their value in the past; in time, values change. Changing economic climates and reevaluation of geologic ideas, may cause some of these resources to be sought by prospectors of the future. For we know that significant resources still remain in the hills as well as a wealth of geologic history.
Geologic Setting
The Medicine Bow Mountains rise as high as 12,013 feet above-sea-level. The adjacent Laramie, Saratoga, and Hanna basins lie at elevations of 6,000 to 8,000 feet. The higher peaks of the Snowy Range which comprise the core of the Medicine Bow Mountains, are pock-marked by numerous lakes left behind by glaciers from the last ice age about 10,000 years ago. These glaciers carved spectacular ridges and valleys in the Snowy Range and carried the rock debris down into the lower valleys. Geologically, this spectacular range represents a Laramide uplift with an ancient core of Precambrian crystalline rock, onlapped by younger, bedded, and less deformed, Phanerozoic sedimentary rock. The range is bounded by faults. Along the eastern flank of the Medicine Bow Mountains, the ancient Precambrian rocks were thrust over much younger sedimentary rocks in the adjacent basins.
The ancient Precambrian rocks of the Medicine Bow Mountains have been studied in detail by Houston and others (1968). This, and later works show the Medicine Bow Mountains to be divided by a major structural feature, known as a suture, that runs roughly east-west to northeasterly through the central part of the Medicine Bow Mountains. In fact, the Snowy Range highway crosses part of this structure near the Nash Fork campground east of the Snowy Range Pass. This suture is expressed as a shear zone that was originally named the Mullen Creek-Nash Fork shear zone. This shear zone is actually part of a much larger shear zone known as the Cheyenne Belt. The Cheyenne Belt has been traced west into the Sierra Madre and is projected to the east under the sedimentary rocks of the Laramie Basin and into the Laramie Range.
On the north side of the shear zone, the rocks are significantly different from those to the south. To the north, the Medicine Bow Mountains are underlain by Archean (greater than 2.5 billion years old) crystalline basement rocks that represent part of an early continental core, or "craton". These very old crystalline rocks are overlain by a very thick succession of younger (2.5 to about 1.7 billion year old) rocks that are predominantly metamorphosed sedimentary rock with minor amounts of volcanic rocks.
The rocks south of the Cheyenne Belt are entirely different from those to the north and consist of younger (2.0 to 1.8 billion years old) intensely deformed and metamorphosed sedimentary and volcanic rock that are now schists and gneisses. These rocks have also been extensively intruded by granite plutons and mafic complexes 1.8 to 1.4 billion years ago.
The Archean crystalline basement north of the Cheyenne Belt (shear zone) is also is exposed in several other mountain ranges in Wyoming as well as in northern Utah, northeastern Nevada, eastern Idaho, large portions of Montana, and extreme northwestern South Dakota, and presumably is hidden under much younger sedimentary rocks in the intervening basins between the mountain ranges. About 2.0 to 2.5 billion years ago, this area represented a small continent with many streams and rivers flowing from the craton into the surrounding oceans.
The younger rocks above the Archean basement north of the Cheyenne Belt were deposited in a basin, or rift, near the margin of the ancient continent. In total, this succession consists of more than 42,000 feet of quartzite, conglomerate, phyllite, and lesser basalt and dolomite deposited in rivers, braided streams, shallow sea water, and scattered volcanoes.
Rocks south of the Cheyenne Belt were originally sedimentary and volcanic rocks deposited in an ocean basin and in volcanic island chains. Before being metamorphosed the rocks consisted of basalt, andesite, and rhyolite flows, volcanic ash, mafic intrusives, shales, and greywackes.
Rocks north of the Cheyenne Belt
A large segment of the Snowy Range highway lies on rock north of the Cheyenne Belt. The rocks north of the Belt are divided into four groups or suites, each of which are farther subdivided into formations (Karlstrom and others, 1983) that lie on a basement of ancient (Archean) gneiss. These groups are in ascending order: the Phantom Lake Metamorphic Suite, the Deep Lake Group, the Lower Libby Creek Group, and the Upper Libby Creek Group.
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| Standing in the Centennial Basin, the author (Dan Hausel) points to the location fo the Centennial Ridge mining district. At the base of the Medicine Bow Mountains is a distinct linear, vegetation anomaly of thicker trees that mark a major fault between the valley and uplifted range. |
The ancient gneissic basement is overlain by Archean (greater than 2.5 billion years old) rocks of the Phantom Lake Metamorphic Suite. These rocks consist of as much as 15,000 feet of metaconglomerate, volcaniclastics, and quartzite exposed along the northern flank of the range. The Phantom Lake Metamorphic Suite is, in turn, overlain by about 8,000 feet of Proterozoic (less than 2.5 billion years old) quartzite and conglomerate, with lesser amounts of mica schist and marble that form the Deep Lake Group. The base of the Deep Lake Group includes uranium-bearing, quartz-pebble conglomerate of the Magnolia Formation (Houston and others, 1977, 1979), described by Houston and others (1968) and Karlstrom and others (1983) as being similar to the uranium ores near Elliot Lake, Ontario. In the Onemile Creek area in the northern Medicine Bow Mountains, Magnolia Formation conglomerates are radioactive and have thin zones with as much as 0.16% uranium.
These conglomerates contain quartzite pebbles in a pyrite-rich matrix. Radioactive minerals are primarily monazite, coffinite, and various uranium and thorium minerals with the chemical characteristics of a mineral called huttonite (Houston and Graff, 1991) (see Appendix 2). Generally, the conglomerate is thought to be fluvial (stream deposited) having been later modified through metamorphism (Snyder and others, 1989). The conglomerate grades laterally and upward into quartzite and is thought to have been deposited in a southwesterly flowing river system draining from a highland to the north.
Rocks of the Deep Lake Group are overlain by the Lower Libby Creek Group which consists of 14,000 feet of quartzite, paraconglomerate, schist, and phyllite. The quartzite formations are very thick and include both the prominent Medicine Peak Quartzite and the Sugarloaf Quartzite which form the spectacular ridges and outcrops atop the Snowy Range. These quartzites retain a number of sedimentary structures such as cross bedding, paleochannels, and ripple marks that are essentially the remains of a river delta.
A major change occurred during the time when the Lower Libby Creek Group sediments were deposited and the time the sediments of the Upper Libby Creek Group were deposited. The rocks of the Upper Libby Creek Group are more varied and were deposited in an open marine (ocean) environment or nearshore. The Upper Libby Creek Group includes stromatolitic dolomite, metabasalt, and black feruginous slate and phyllite. Typically, these rock typess are formed in shallow water intertidal flats, with the exception of the feruginous slate that is more characteristic of relatively deep oceanic environments.
Rocks south of the Cheyenne Belt
South of the Cheyenne Belt, the Medicine Bow Mountains are made up of a complex of quartzofeldspathic gneiss and interlayered hornblende gneiss and amphibolite. These have been intensely deformed and recrystallized by metamorphic processes making it difficult to determine their precursors, and ultimately, how they originally formed. Most likely, they were deposited as mafic intrusive rocks and basaltic, andesite, and rhyolite flows and volcanic ash layers (tuffs) from volcanos, shales, and greywackes (micaceous sandstones). They were later intruded by several igneous masses and plutons including the 34 square mile Keystone quartz diorite, gabbro dikes, some granite and quartz monzonite plutons, the 60 square mile Mullen Creek mafic complex and the 25 square mile Lake Owen mafic complex (Houston and others, 1968).
Assuming rocks south of the Mullen Creek-Nash Fork shear zone in the Medicine Bow Mountains are similar to those exposed south of the Cheyenne Belt in the nearby Sierra Madre range to the west, we can better appreciate and understand the less well-preserved rocks in the southern Medicine Bow Mountains. These rocks south of the Cheyenne Belt in the Sierra Madre are a variety of relatively well preserved metamorphosed volcanic and sedimentary rocks which include basalt, andesite, and rhyolite flows as well as tuffaceous rocks, shales and greywackes. Even evidence of volcanic vents have been found. These rocks are typically found in or adjacent to volcanic island arcs.
Areas of Interest
The Medicine Bow Mountains encompass a large mountainous uplift of more than 900 square miles of which the Snowy Range is only a small part. The Snowy Range is generally considered to encompass only those high perennial snow-covered quartzite peaks near the summit of the scenic byway. The remainder of the Medicine Bow Mountains also has many interesting areas and many campgrounds. Some of these areas have paved roads and other areas are accessible by graded roads and trails. You may want to contact the U.S. Forest Service for information on roads and conditions. The Forest Service has district offices in Laramie, Encampment, and Saratoga as well as a seasonal information center located one mile west of Centennial (see Plate 1). Maps of this area are available from the Forest Service. Detailed topographic and geologic maps of the Medicine Bow Mountains are available from the Geological Survey of Wyoming on the University of Wyoming campus in Laramie. Additionally, the Survey has a small contingent of geologists who are available to help you identify any rocks you might pick up in Wyoming.
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| The author poses after shoveling snow in June, 1993. Well, not really. This is a photo of the author in front of a snow drift mined by the State Highway Department along Highway 130 in the Medicine Bow Mountains. So, global warming again missed Wyoming and makes rock hounding in the Snowy Range an alpine sport. |
During your drive along the Snowy Range Scenic Byway (State Highway 130), you will pass many interesting rock formations and features. I've selected some of the more interesting places that you may want to stop for a short period of time and take a closer look. Be sure to take your camera. I have also selected several localities of historical and/or geological interest outside the Scenic Byway within the Medicine Bow Mountains and adjacent areas that I think you'll enjoy.
Locality 1- Gateway to the Snowy Range: Anywhere along the Snowy Range highway from about 1 mile west of the Herrick Lane (State Highway 12) turnoff to the Overland Trail turnout (Locality 2) is a good place to view the gateway to the Snowy Range and the Medicine Bow Mountains.
In the foreground only a short distance south of the road and the nearby fence is Big Hollow. This huge wind excavated valley (basin) covers an area of more than 25 square miles and is about 9 miles long, 3 miles wide, and 150 feet deep. No streams or rivers drain the basin (Hausel and Jones, 1984). The basin probably formed by strong winds that have persisted in the area over a long period of time. Similar, but smaller wind deflation features are found at a number of sites along the western edge of the Laramie Basin. Many of these are now filled with water, such as Lake Hattie and Porter Lake.
Locality 2- Overland Trail historical marker: Look for the turnout on the north side of the highway. The Overland Trail was used extensively between 1862 to 1868, but Larson (1990) points out that the trail was also used as late as 1900, but to a lesser degree. The trail ran from the Laramie plains, skirted the northern Medicine Bow Mountains, turned southwestward into Saratoga, and continued westward through the Greater Green River Basin to Fort Bridger in southwestern Wyoming.
In 1876, gold was discovered in the loose dirt of the Overland Trail near the present site of Arlington. A gold rush to the area led to hydraulic gold placer mining. The mine operations were sporadic and reported in this area in 1877 and in 1897 (Hausel, 1993). Evidence of one of the historic gold mines is found in Emigrant Gulch immediately north of Interstate-80, one mile west of Arlington. Gravel tailings piles, washed by Giants (hydraulic monitors), mark the site of the historic operations in Emigrant Gulch. The Overland Trail is visible within a few yards east of the gravel piles.
Fort Halleck (1862-1866) was built at Elk Mountain further to the west at the north end of the Medicine Bow Mountains to provide protection for travelers on the trail, and was later abandoned when Fort Fred Steele was established further to the west along the Platte River. One of the more famous passengers of the Overland stage line which used the trail was Mark Twain, who described some of his experiences in the western classic Roughing It.
Locality 3- Big Hollow oil field: The Big Hollow oil field can be seen by looking south from Highway 130 at the intersection of State Highway 130 with Albany County Road 44. Discovered in 1938 and is currently producing oil from the Muddy Sandstone (Early Cretaceous) at a depth of 800 feet. The oil is structurally controlled in the Big Hollow anticline (Hausel and Jones, 1984).
Locality 4- Table Mountain: Table Mountain is the prominent, flat-top hill about 1 mile south of the highway. This hill is an erosional remnant of the Table Mountain pediment surface (Hausel and Jones, 1984).
Locality 5- Titaniferous black sandstone: Near the base of Sheep Mountain, about a mile south of Highway 130, is a small, 4- to 6-foot-high, low-lying dark outcrop. The outcrop is formed of titaniferous black sandstone of the Mesaverde Formation (Late Cretaceous).
The sandstone is up to 17 feet thick, 50 feet wide, and has been traced for 4,300 feet along the northeastern edge of Sheep Mountain using a magnetometer (Hausel and Jones, 1982). The sandstone represents a fossil beach placer that was formed along the edge of an ancient sea 63 to 90 million years ago. Relatively heavy minerals (many which are black and opaque) were concentrated at the prehistoric shoreline by wave action.
The sandstone is rich in magnetite and zircon, and contains ilmenite with minor amounts of rutile, sphene, monazite, garnet, spinel as well as anomalous gold (Houston and Murphy,1962). These titaniferous black sandstones are considered to be important sources for a number of strategic metals including titanium, iron, zirconium, rare earth elements, and gold.
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| Outwash plain (boulder field) from a glacier from the last ice age. This area of the Centennial Valley is covered by an extensive boulder field that originated in the high peaks of the Snowy Range (photo by Sheila Roberts). |
Locality 7- The town of Centennial was a gateway to mining and logging activities in the Medicine Bow Mountains in the late 1800s. Founded in 1876, the town was named in honor of the Nation's Centennial anniversary. Today, Centennial is the home for about 100 residents. Many summer cabins, houses, a museum, and a few cafes form much of the town.
Locality 8- Centennial Ridge is the prominent ridge that abruptly rises from the basin floor immediately west of Centennial. Gold was discovered along Centennial Ridge in 1874, and was also found in the Middle Fork of the Little Laramie River even earlier. A short time later in 1876, the Centennial Ridge mining district was organized.
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| Remains of the early gold rush in the Centennial Ridge mining district. The Queen mine headframe as it appeared in 1980 on top of Centennial Ridge, is a reminder of a by-gone era. |
Both lode (vein-related) and placer (stream transported) gold and platinum have been found in the Centennial Ridge district (McCallum, 1968; Hausel, 1989). The lode gold generally occurs in quartz veins hosted by mica and hornblende schist and gneiss, and the lode gold-platinum occurs as fracture fillings and replacements in faults and shear zones in the schist and gneiss (McCallum, 1968). Gold and platinum are commonly associated with pyrite (a brittle, metallic, bronze-colored, iron sulfide) referred to as fool's gold by prospectors, and arsenopyrite (a metallic, silver-colored, arsenic-iron-sulfide). Placer gold and platinum generally occur as small flakes known as colors along Fall Creek and the Middle Fork within the district. Nuggets are uncommon.
Locality 9- Centennial mine: The adit (tunnel entrance) of the Centennial mine is hidden in the trees west of the town of Centennial, but a small prospect pit can be seen above the adit. The Centennial claim was staked in 1875, and within a short time gold was being mined from the Centennial lode. As the ore was mined, it was hauled out of the tunnel in ore cars, dumped into buckets suspended from a tramway at the mine adit, and lowered 260 feet down into the valley along a 425-foot-long tramway (Duncan, 1990). At the base of the tramway, the ore was received in a 10 stamp mill where it was crushed and processed. Much of the gold was recovered on amalgamation plates where the gold combined with mercury. The mercury-gold amalgam was later retorted (heated in an enclosed cylinder) to separate the gold from the mercury. However, much of the refractory gold occurring in pyrite could not be recovered by this method and was lost in the tailings.
In the summer of 1877, the Centennial drift drove from the rich vein into a gouge zone in barren, gray, hornblende gneiss. The vein was offset by a fault! The extension of the lode could not be found and operations terminated. Even to this day, modern exploration techniques have not been attempted to locate the extension of the lode.
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| Panning for gold on the Middle Fork of the Little Laramie River near the Centennial Mining district. Didn't find any gold, just lots of pyrope garnets (a diamond indicator mineral) from a buried kimberlite pipe somewhere up stream. |
Locality 10- Platinum City: Later (about 1930), minor to trace amounts of platinum were found in some ores in the Centennial Ridge district. Some mines reopened including the Platinum City mine south of the Centennial and Utopia gold mines. However, the rebirth of the district was only short-lived.
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| The historic Platinum City mine, viewed from Centennial Ridge. |
The platinum values were apparently greatly exaggerated by a local promoter who began to lay out plans for a town called Platinum City about 2 miles south of Centennial along the Union Pacific Railroad right-away. The mine above the town was named the Platinum City mine. But the mine and the townsite were doomed from the beginning, and the promoter was indicted in mail fraud related to the exaggerated stories of unusually rich platinum ore (Thybony and others, 1985).
Locality 11- Snowy Range Lodge (Libby Lodge): If you drive along the Barber Lake Road (Forest Service Road 351), you will pass an old log lodge on the south side of the road. Construction on this lodge began in 1924 and included 17 rooms on the second and third floors. The main floor was used for dining and offices, and included a dance hall and kitchen (Thybony and others, 1985). Today, the lodge serves as a private residence with the main floor available for various celebrations and events. The current residents have taken great care to restore and preserve this historic structure.
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| Spectacular folded slate along highway. |
These rocks are intensely deformed and metamorphosed such that it is difficult to determine how they originally formed. However, based on the rock mineralogy, geochemistry, and geological setting, most likely these were originally greywackes (micaceous sandstones) (Snyder and others, 1989). The intense deformation and metamorphism that these rocks were subjected to, resulted in the melting of portions of the rock, producing aluminous granites, dikes, and veins. The veins are often folded and typically have been stretched in the vertical plane producing boudins (link sausage-like morphologies).
Locality 13- Medicine Bow ski resort: The Medicine Bow ski resort south of the highway (Figure 14), is open to the public during the winter months. This is the only active ski resort in southeastern Wyoming. The resort opened in 1960 (Thybony and others, 1985).
Locality 14- Mullen Creek-Nash Fork shear zone: Fifty to 100 yards south of the highway is an exposure of sheared gneiss cropping out in the south bank of Telephone Creek west of the Wilderness camp (formerly, the University of Wyoming's S.H. Knight science camp). The gneiss is part of the Mullen Creek-Nash Fork shear zone which is poorly exposed in this area. The shear zone is part of the Cheyenne Belt that separates younger rocks to the south from older rocks to the north.
The gneiss is deformed with abundant parallel fractures and microfractures producing mylonite which is cut by some coherent pink, folded, felsic layers. Movement along the shear zone (fault) occurred between 1.73 and 1.64 billion years ago (Hills and Houston, 1979).
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| Folded French Slate at the Nash Fork campground. An early folding event produced tight (isoclinal) folds with parallel limbs. These were later refolded by open buckle folds. This same outcrop has many spectacular crenulated beds (chevron folds) produced during refolding. |
There is evidence of glaciation at this stop. The outcrop of the folded, dark, French Slate has some large, white, quartzite boulders (erratics) sitting on it. During the Ice Age, these boulders were carried by a glacier from the Snowy Range ridge area and deposited here when the ice melted.
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| White, glacial-erratic quartzite boulders sit on dark French Slate adjacent to the Nash Fork campground. These boulders were dropped by a melting glacier from the Medicine Bow Peak area 3 to 4 miles to the west. Just one of dozens of known climate change events that occurred in the geologic past (Hausel, 2018). |
Locality 17- Sugarloaf recreation area: A small Forest Service sign on the north side of the Snowy Range Highway marks the turnoff to the Sugarloaf recreation area. Turn here and drive north along the graded road. The road will cross two small creeks within a quarter of a mile of the turnoff. After crossing the second creek continue about 0.1 to 0.2 mile. On the right side (east) of the road, is a grayish-tan to tan outcrop. This is metadolomite of the Nash Fork Formation (Upper Libby Creek Group) which contains fossil evidence of some of the oldest life on the surface of the earth, known as stromatolites. Stomatolites are layers of carbonate material (originally arranged in horizontal mats, domes, collumns, or semispheres) deposited in shallow marine water by the influence of blue-green algae. Colonies of the algae trapped fine silty detritus and precipitated calcium carbonate bioherms (domes) and reefs.
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| Stromatolite domes of the Nash Fork Formation deposited in an ancient ocean more than 1.7 billion years ago. Using shapes of the bioherms, it is possible to determine which way was up when these were initially deposited. The v-shaped limbs of the bioherm point to the ground at the time of deposition, thus the top of the unit was to the south. These rocks have been tilted through geologic time. |
Locality 18- Lewis Lake and the Billie Class stamp mill: From the stromatolite outcrop, drive north around the hill and Libby Lake will appear on the left side (west) of the road. Continue north around the eastern shore of the lake to the Lewis Lake parking lot. From the parking lot, follow the hiking trail around the edge of Lewis Lake to the north shore. On the north shore lies the remains of the Billie Class three stamp gold mill used sometime between 1890 and 1920 to recover gold from sheared, pyritized hematite-chlorite-schist in the Lookout Schist (Lower Libby Creek Group).
As you walk around the old mill site, you will see several prospect pits and trenches. Even today, some greenish, copper-stained rock can still be found 100 to 200 yards east of the mill, and bronze-colored pyrite ("fool's gold") occurs in pyritizied schist 50 to 100 yards west of the mill. An iron-stained gossan (rusty rock) altered zone is traceable for 2,000 feet along an easterly trend.
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| Sample localities where we found gold and diamond indicator minerals at the Centennial Ridge area. |
Along the southwestern shore of Lewis Lake, a radioactive quartz vein yielded a sample of rock that contained 0.1% uranium, 0.16% thorium, and 0.004 ounce per ton gold (Houston and others, 1983).
Locality 19- Northwest shore of Lewis Lake: West and a little south of the Billie Class stamp mill is an interesting outcrop of paraconglomerate on the side of the hill on the northwestern shore of Lewis Lake.
The outcrop is formed of rounded to angular pebbles and cobbles of quartzite, schist, and gneiss in a dark gray to blue-gray matrix. Blackwelder (1926) suggested these conglomerates represent tillites deposited along the edge of a glacier during an ice age more than 1.7 billion ago. Alternatively, the paraconglomerate could represent a landslide (Houston and others, 1968, p. 25).
Locality 20- Libby Flats observation point: The observation platform and adjacent parking lot on the south side of the road are located on metadolomite of the Nash Fork Formation (Upper Libby Creek Group). Libby Flats is the open grassy terrane south and of the observation deck. The area surrounding the observation platform was once known as the LaPlata mining district which included a number of small prospects and mines as well as the Lewis Lake gold deposit (Locality 18), the Red Mask mine (Locality 22), the Bellamy Lake copper prospect (Locality 23), and the prospect lying about a quarter of a mile to the south (Locality 21). The mines and prospects in this district where never developed to any great extent because most of the rocks were poorly mineralized. Although, Duncan (1990) discussed rich silver lodes in this district, we were unable to find any samples with significant silver values to verify the historical reports.
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| Snowy Range Ridge cut into Medicine Peak Quartzite |
Locality 21- Libby Flats prospect: About a quarter of a mile south of the Libby Flats observation point, along a jeep trail, are the remains of an historical cabin which marks the site of an old prospect. The prospect is in brecciated metadolomite of the Nash Fork Formation and consists of angular metadolomite clasts cemented by massive and boxwork limonite. The limonite boxworks are butterscotch- to tawny-colored, spongy and porous, iron oxides that represent the remains of iron carbonate (siderite). In other words, much of the former iron carbonate has been leached from the rock leaving open pore spaces (vugs) in place of the former crystals. The matrix surrounding the vugs has been replaced by limonite. A sample of the boxworks collected from the prospect by the author contained no detectable gold or silver.
Turn a little bit to your right and look directly north. About a mile distant is a symmetrical, white hill that almost looks like a mound of sugar. This is Sugarloaf Mountain formed of Sugarloaf Quartzite (Lower Libby Creek Group) which is located west of Libby and Lewis Lakes. The highest point on the Snowy Range ridge just to the left of Sugarloaf Mountain is Medicine Bow Peak.
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| Sketch of the Red Mask mine by W. Dan Hausel. |
Locality 23- Bellamy Lake copper prospect: Like the other lakes in this area, Bellamy Lake occupies a small, shallow, glacially-carved basin. Fifty to 100 yards northwest of the lake shoreline, is an old copper prospect located on a contact between fractured Sugarloaf Quartzite and a dike of mafic (dark) igneous rock. Minor amounts of quartz with some chalcopyrite (a bronze, metallic, copper pyrite) can be found in chlorite schist. The chlorite schist is part of the mafic dike. A sample of the schist collected by the author contained no detectable gold, 0.02 ounce per ton silver, and only 0.04% copper.
Locality 24- Mirror Lake: Mirror Lake fills a glacially-carved basin in the Sugarloaf Quartzite. Outcrops of this quartzite form the low-lying ridges on the north side of the lake. Spectacular outcrops of the Medicine Peak Quartzite form the prominent white cliffs in the background.
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| Hard quartzite containing rounded quartz pebbles part of a paleo-placer in the Medicine Bows. |
Lake Marie has two parking lots connected by a paved walking path. The Lookout Schist crops out near the stone building adjacent to the western parking lot. A few yards east of this building, the schist is folded and exhibits prominent axial plane cleavage.
Adjacent to the parking lot along the eastern shore of the lake is a field of boulders with rocks from both Medicine Peak Quartzite and Sugarloaf Quartzite. The Medicine Peak Quartzite is a medium-to coarse-grained white quartzite with layers of quartz-pebble conglomerate. The quartzite contains minor grains of sericite (white to silver-colored mica), black tourmaline, and light-blue transparent kyanite. The Sugarloaf Quartzite is also a monotonous white, medium-grained quartzite with minor sericite and black tourmaline.
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Quartz-pebble conglomerate bed in quartzite boulder
on the eastern shore of Lake Marie. |
Some sedimentary structures preserved in the quartzite boulders provide geologists with clues on the depositional environments. Some of the boulders have bedding, cross bedding, and occasional beds of quartz pebble conglomerate. These suggest the Medicine Peak Quartzite was deposited in a river bed or in the subtidal portions of a delta or an estuary. Paleocurrent directions from quartzite outcrops elsewhere, indicate the sediment that forms the quartzite was carried by water in a west- to southwest direction. This implies there was a highland source area to the northeast more than 1.7 billion years ago that supplied the sediment. The presence of small scale oscillation ripples in the quartzite also suggest some of the quartzite was deposited as quartz sandstone in shallow water along the edge of an ancient ocean.
Locality 26- Snowy Range ridge and Medicine Bow Peak: Medicine Bow Peak on Snowy Range ridge is the highest point in the Medicine Bow Mountains (12,013 feet) (See locality 22). A trail to the top of the peak is usually accessible by late summer and early fall.
Locality 27- Road to the Gold Hill mining district: Turnoff to the Gold Hill mining district. Forest Service Road 293 to the Gold Hill district is not designed for automobiles and should not be attempted without a 4-wheel-drive vehicle with good clearance. The historical district is about 2 to 2.5 miles north of the Snowy Range highway.
Locality 28- Gold Hill district: the Gold Hill mining district was organized in 1890 following the discovery of rich gold-quartz veins in the previous year. The veins were generally poorly mineralized with sporadic, small and discontinuous, ore shoots (rich pockets of gold). However, some specimen grade material taken from an ore shoot in the Acme mine reportedly assayed as high as 2,100 ounces of gold per ton (based on the 1992 prices for gold, the contained metal in a ton of this specimen grade rock would be worth $735,000 to $850,000). Gold placers in the district were few and restricted in size.
Unfortunately, the gold was not consistently distributed throughout the veins. This, coupled with the narrow vein widths, resulted in the closure of the mines within a few years. Total production from the district is unknown, and was estimated to have amounted to only about 145 ounces by 1893. Actual production was probably a few times this figure.
The district lies on a north-northeast plunging anticline in Proterozoic metasedimentary and metavolcanic rocks (Karlstrom and Houston, 1979). The core of the anticline is formed of rocks of the Phantom Lake Metamorphic Suite, which includes quartz-pebble conglomerate, quartzite, phyllite, and metavolcanic rocks. This core is overlain by rocks of the Deep Lake Group which includes the Magnolia Formation (conglomerate and quartzite) and the Lindsey Quartzite.
Today, little remains of the historical mining operations other than the old mine workings, a few decaying log cabins, and rusting steam boilers. Ocassionally, some attractive gold specimens are still found on the historical mine dumps.
Locality 29- Gold Hill ghost towns: According to Duncan (1990), a few townsites were organized during the gold boom at Gold Hill. The Gold Hill townsite was located in the southern part of the district and was bordered by the Gold City townsite on its northwest.
Two other townsites (Golden Courier and Greenville) were also built. Of these two, Greenville in 1891 included 10 log cabins, 20 tents, two hotels, and a saloon. One of the hotels, the Acme Hotel, was a two story structure with 14 rooms. In total, the Gold Hill townsites included three hotels, three saloons, a blacksmith shop, a post office, several log cabins and tents (Duncan, 1990). Today, only a few scattered decaying cabins are all that remain of the historic town sites.
Locality 30- Vagner Formation paraconglomerate: Some good exposures of the Vagner Formation paraconglomerate occur immediately west of Dipper Lake on a 4-wheel-drive road (Forest Service Road 103) that forks from the Gold Hill road and runs to the north. The paraconglomerate crops out on the south flank of a small hill a few yards above a couple of prospect pits. The paraconglomerate is dark gray with numerous white granitic pebbles and cobbles.
Locality 31- Ryan Park (Barrett Ridge) ski area- No longer in use, the old ski runs south of the road are difficult to see, and have been partially reclaimed by a new growth of pine trees. The ski resort was opened in the winter of 1941-1942 with the aid of the Saratoga CCC camp. The resort was serviced by a 40 chair chairlift. Operations ended in the 1960s (Thybony and others, 1985).
Locality 32- Brush Creek-Mullison Park gold placers: The Brush Creek-Mullison Park area had a very interesting early gold prospecting history (Thybony and others, 1985, p. 93-94). This area was prospected in the late 1800s following the discovery of gold flakes and some small thumb-nail size nuggets in the creeks. According to Mullison (1909) (an early prospector in the Medicine Bow Mountains) in 1870 some Ute Indians described several ancient prospects in the upper North Brush Creek basin. Mullison later investigated these prospects in 1886 and found several diggings no more than half a mile apart on North Brush Creek, Cortez (also known as Cortex) Creek, and Mullison Creek (named in honor of the prospector).
Mullison described these diggings as relatively old prospects possibly dug by the Spanish. At one location near the mouth of Cortez Creek, Mullison reported that a 67-foot deep shaft sunk in 1886 intersected some older mine workings that contained a tunnel and a 4-foot diameter shaft. The workings were in very poor condition, but before leaving, Mullison found an artifact of a face carved in "elk's ivory" on the floor of the mine. This was in the SW section 34, T17N, R81W (Locality 34). Similar workings were also reported to the southeast in sections 10 and 11, T16N, R81W, along Mullison Creek (Locality 33). Duncan (1990) suggested that it was possible that some of these prospects were dug by Forty-niners on their was the the Californian gold rush.
In the same area (Locality 33), Mullison described an old stone wall along the creek, built to keep the steep bank from caving. Five separate prospects were found near the wall. A short distance from these prospects, Mullison found a 6-foot diameter circular shaft sunk in an abandoned part of the creek bed. Trees growing on top of the mine tailings were estimated to be more than 175 years old (Mullison, 1909, p. 32) suggesting the mine may have been of Spanish origin.
An article from the Saratoga Sun (Anonymous, 1932) reports on more interesting history for this area. Apparently, a prospector named Bradfield found an unusually rich gold placer in 1864, assumed to be in the vicinity of Brush Creek (although the newspaper article reported that the prospect could instead have been in the Cedar Creek drainage). A cursory description of the surrounding area, stated that,"the soil of this gulch was a gravel formation, red in color". Bradfield dug through 8 feet of gravel before intersecting "slate" bedrock. The "slate" was cut by long, irregular crevices literally filled with gold flakes. In two days, Bradfield recovered 4 ounces of gold before being attacked by Indians. In a narrow escape, Bradfield abandoned his supplies and tools, including his pick and shovel. Upon returning to the area with group of well-armed prospectors, Bradfield searched in vain, but could not find the exact location of what became known as the "Lost Pick and Shovel prospect".
Locality 33- Mullison Creek: Mullison Creek and Lincoln Creek both have historic gold placers. Nearly every year, small quantities of gold including tiny nuggets are recovered from this area.
Locality 34- Cortez Creek placers: Cortez Creek (erroneously known as Cortex Creek on Forest Service maps) drains into North Brush Creek off of Hanna Formation (Tertiary) conglomerates. The drainage has been worked several times for placer gold (see Locality 32), as is evident from an old sluice and some hose fragments from a hydraulic mining operation.
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| Placer diamonds from Cortez Creek found by Paul Boden in 1977. The larger diamond weighed 0.1 carat and the other weighed 0.03 carat. Scale is in millimeters. |
Locality 35- Outcrop: On the north side of the road are prominent gray to pink outcrops of quartzofeldspathic gneiss. These rocks may represent the oldest rocks in the Medicine Bow Mountains and are assumed to be more than 2.5 billion years old. The gneiss is cut by a narrow, black, gabbro dike that can also be seen in the road cut.
Locality 36- Saratoga townsite and hot springs: The town of Saratoga is locally known for its hot springs and geothermal artesian wells. Breckenridge and Hinckley (1978) describe several springs emanating from the Tertiary North Park Formation in the Saratoga area, although the geochemical characteristics of the water suggest a deeper aquifer is involved. The springs line up on a northeasterly trend, which strongly suggests they are fault controlled.
The best known of the springs is the Hobo Spring in the Saratoga Hot Springs City Park, where a dirt-floored spring is protected from flooding from the adjacent North Platte river by a masonry wall. The spring is accessible to the public at no cost. The water temperature measured in 1976 was 118°F (Breckenridge and Hinckley, 1978, p. 13).
Locality 37- Encampment townsite: Home of Wyoming's historic copper boom. Today, Encampment is primarily a logging town. The town includes the Grand Encampment museum which contains exhibits and has a wealth of information about the late 1800s and early 1900s copper boom.
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| Historic photo of the Ferris-Haggarty mine, Sierra Madre Mountains. This once prosperous copper-gold-silver mine likely still contains considerable amounts of unmined gold and copper. |
Some unfortunate events forced the closure of the Ferris-Haggarty mine even though the deposit was not mined out. First, the concentrating mill at Riverside was destroyed by fire in 1906. In the following year, a large part of the smelter was also destroyed by fire. The final nail in the coffin occurred in 1908, when the price of copper declined 35% from $0.20 per pound to $0.13 per pound.
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| Inside the Ferris-Haggarty gold-copper-silver mine, Sierra Madre Mountains. Note there is still considerable unmined copper (green and metallic) in the ribs of the mine. The characteristics of this outcrop suggest that these rocks were deposited in an ancient, volcanic, submarine vent. Such deposits are sometimes very rich and were termed "millrock" by Canadian geologists since they were almost always found near an operating mill and mine in similar rocks in Canada (photo by the author). |
Total production from the Ferris-Haggarty mine is not accurately known. However, the U.S. Bureau of Mines reported metal production from the Encampment district from 1898 to 1911 was 21,800,780 pounds of copper, 29,318 ounces of silver, and 2,237 ounces of gold (see Hausel, 1989, p. 152). Most of the metal production came from the Ferris-Haggarty mine.
The ore body at the Ferris-Haggarty mine averaged 6 to 8% copper with high grade ore carrying from 30% to 40% copper with some gold and silver. The deposit was described as 20 feet thick, occuring in quartzite breccia of the Magnolia Formation along the contact of hanging wall (overlying) schist and footwall (underlying) quartzite, and continuous downdip for at least 400 feet. In 1904, A. C. Spencer of the U.S. Geological Survey reported the extent of mineralization had not yet been determined.
Many years later, during the second world war, the Ferris-Haggarty mine was investigated by the War Minerals Board and found to have had large blocks of unmined low-grade ore (averaging 5% copper). The historical mine workings were so extensive, that the geologists had to make maps as they investigated the deposit so they could find their way out to the surface each evening (Ralph E. Platt, oral communication, 1989).
Locality 38- Riverside: Riverside is a small community next to the town of Encampment along the Encampment River. This was the site of the Boston-Wyoming smelter and concentrating mill that processed ore from the Ferris-Haggarty copper mine. A tramway was built from the Ferris-Haggarty mine to the smelter and had a daily haulage capacity of 984 tons, whereas the smelter had a maximum daily capacity of only 500 tons of ore (Figure 32). Today, nothing remains of the smelter and concentrating mill.
Locality 39- Purgatory Gulch: It was reported by the Chicago Herald in 1897 that a rush began following the discovery of gold in the Purgatory Gulch area of the Encampment district (Larson, 1990). A few years later Henry C. Beeler, Wyoming State Geologist, reported "some remarkably rich gold specimens were found here" (Beeler, 1905).
The Purgatory Gulch area lies south of the town of Encampment. The area itself is accessible by jeep trail a short distance of a graded road. Several small gold mines and prospects are found in the gulch and on the adjacent hillsides. In 1989, I collected a grab sample of quartz containing visible gold from a mine on top of the hill west of Purgatory Gulch overlooking the Encampment River. A general rule of thumb is that if you can see visible gold in quartz, the sample will generally assay at least 1.0 ounce per ton in gold. A second sample with pyrite in quartz was assayed yielding 0.55 ounce per ton gold, 0.12 ounce per ton silver, and 0.01% copper (Hausel, 1989, p. 157-158).
A quarter of a mile up stream from the mouth of Purgatory Gulch, where it is intersected by an unnamed gulch, are the remains of several log cabins. This ghost town was the home of the miners who worked in Purgatory Gulch.
Locality 40- Big Creek district: A few small mines and prospects were developed on copper-bearing and rare earth-bearing pegmatites in the Big Creek mining district. The pegmatites are hosted by layered gneiss and schist.
Locality 41- Big Creek mine: The Big Creek mine is in a 15- to 20-foot wide, copper-bearing feldspar pegmatite traceable on the surface for 2,400 feet. The pegmatite is exposed in the canyon rim along Big Creek; 70 feet below the rim, the pegmatite contains chalcopyrite, bornite, chalcocite, malachite and chrysocolla (Houston, 1961).
Locality 42- Platt mine: The Platt mine was developed in a 70- by 160-foot thick rare earth-bearing pegmatite. The pegmatite, which is a coarse grained granite, consists of feldspar, mica, quartz, and rare earth minerals. It is exceptionally rich in rare earths and yielded 10,000 pounds of euxenite from 1956 to 1958 . In addition to euxenite, the pegmatite has some other rare earth element-bearing minerals; notably monazite and columbite (Houston, 1961).
Locality 43- Natures Mint mine: The Natures Mint mine, a historic gold mine along Boat Creek, is accessible from Forest Service Road 512. The mine workings continue across the road following a narrow quartz vein. During one recent study, McCallum and Kluender (1983) selected a sample of quartz from this vein that assayed 23.3 ounces of gold per ton!
Locality 44- Keystone Mining district: This district lies along Douglas Creek in the vicinity of the village of Keystone. The district is accessible by Forest Service Roads 500 and 542 west of Albany. Albany can be reached via State Highway 11 which begins about 5 miles east of Centennial. The Keystone village originally included several mine employee cabins and support buildings (Locality 45). Some of these early structures have been converted into summer cabins.
Several active gold mines and a few copper mines were centered in the district in the late 1870s (Hausel, 1989). The principal lode was the Keystone-Florence trend which ran from the village of Keystone to the Florence mine nearly a mile to the southeast. The Keystone mine was sunk on the northwestern end of this trend and the Florence mine developed on the southeastern end. Mineralization along the trend varied from trace to anomalous amounts of gold, with ore shoots located at either end of the lode.
The geology of the district is dominated by a large, circular, 5-mile diameter, quartz diorite pluton that intrudes quartz biotite schist and amphibole gneiss. The principal ore bodies are found in tensional shears (faults) subsidiary to the Mullen Creek-Nash Fork shear zone (Currey, 1965). These mineralized shears range in thickness from a few feet with local splays to over 300 feet (Loucks, 1976).
Locality 45- The Keystone mine: The Keystone lode was originally staked in 1876 and later developed into a mine. The shaft was sunk in quartz biotite schist along the northwestern flank of the Keystone quartz diorite. Available reports estimate about 5,000 ounces of gold were recovered from the mine before operations ceased in 1893.
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| Historical Keystone gold mine and mill. A small headframe situated over the mine shaft, to the right of the mill behind a cabin, was used to haul ore to the surface. Immediately left of the four story mill building is the Douglas Creek drainage (photo from the University of Wyoming American Heritage center, S.H. Knight collection). |
Cleanup operations around the mine and mill occurred between 1916 and 1939, and the mill was later dismantled in the 1950s (Currey, 1965). Sometime during this period, much of the remaining ore on the dump was probably processed, since very little of the ore can be found on the mine dump presently.
Some gold is still found in this region each year. In the mid 1970s, Loucks (1976) collected samples from the Keystone mine that assayed from 0.19 to 8.75 ounces of gold per ton. Recently, the author collected samples from the mine dump and in the Keystone shear zone that yielded none to 0.64 ounce of gold per ton.
Locality 46- Florence mine and ghost town: Located at the southeastern end of the Keystone trend. The Florence lode is entirely within Keystone quartz diorite. The lode claim was not recorded until 1882, although the mine was presumably worked prior to that time (Duncan, 1990, p. 109). According to Currey (1965), the Florence mine produced an estimated 2,500 ounces of gold.
The available reports indicate the Florence had pockets of pyrrhotite (iron sulfide) with considerable gold. These sulfide "kidneys" contained as much as 7.5 to 48 ounces per ton of gold (Currey, 1965). This was more or less verified by Loucks (1976) who collected samples from the property that contained from 0.06 to 23.3 ounces per ton of gold. The author also collected samples from the Florence mine that varied from none to 1.3 ounces per ton gold. One small boxwork sample with several visible specs of gold was not assayed but was instead donated to the owner of the mine property. Based on the amount of visible gold in the sample it would have undoubtedly assayed several ounces of gold per ton.
Today, the remains of several abandoned cabins at the Florence mine site are all that remain of a former townsite. According to Duncan (1990, p. 115) as many as 30 people lived at the Florence mine townsite in 1878. The town also included a boarding house known as the Miners Hotel.
Locality 47- Gold Crater mine and ghost town: Behind (north) the Forest Service work center along Forest Service Road 542 are several old mines including the Gold Crater shaft. The shaft was sunk in the southeastern edge of the Mammoth trend; about 3/4 mile to the northwest on the same trend is the Independence copper-gold mine. The Gold Crater lode consists of several sheared quartz veins containing pyrite, chalcopyrite, and free gold.
Seven samples collected from mines in the Gold Crater Group by the Geological Survey of Wyoming, contained none to 0.03 ounce per ton gold, and none to 0.55 ounce per ton silver. Two samples yielded 0.04 percent and 0.2 percent copper, and two other samples had 0.025 percent and 0.032 percent cobalt. The assays indicate the rock is weakly, although anomalously, mineralized. A short distance west of the Gold Crater mine are the remains of several cabins and associated artifacts belonging to an old mining town.
Locality 48- Douglas mine and dredge tailings: Forest Service Road 543 from Keystone to Rob Roy Reservoir runs directly over the now buried 150-foot-deep shaft of the Douglas mine (Figure 34). This shaft was sunk on a mineralized vein reported to be 7 feet wide on the 35 foot level. Native copper, malachite (copper carbonate), chalcopyrite (copper-iron-sulfide), chalcocite (copper sulfide), cobaltite (cobalt-iron-sulfide), and gold were all found in the vein. At deeper levels, the vein split into three veins (0.5 to 2 feet, 2 to 3 feet, and 1 foot thick) (Currey, 1965). The presence of cobaltite is especially interesting. Cobalt is rare in the United States and is a critical strategic metal with important applications in high-tech jet fighters and in missiles including the Patriot missile.
East of the former Douglas shaft are dredge tailings piled along Douglas Creek that mark the site of the Moe Brothers 1958 dragline and floating washing plant placer gold operation. The Moe Brothers Gold Run placer is actually part of the Douglas Creek placer mining district (see Locality 49).
Locality 49- Douglas Creek placer mining district: Douglas Creek begins near Willow Park south of Libby Flats and flows south through Rob Roy Reservoir and the Keystone district for several miles before swinging northwesterly and drains into the North Platte River. This creek and many of its tributaries cut across gold and platinum lodes and tends to concentrate precious metals into pockets or paystreaks in the stream bed. The district, which covers many miles of streams, was initially called the Foley district, but was renamed the Douglas Creek district in 1876 (Figure 35) (Duncan, 1990, p. 107).
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| Circa 1905 steam shovel along the side of long tom (sluice box) on the Home placers in the Douglas Creek mining district. The largest nugget discovered prior to 1906 was 3.4 ounce pebble of gold found on the Home placers |
Natural reclamation through time has removed nearly all evidence of these early (pre-1900) placer mining operations. Occasionally, evidence of an early flume is found, but many flume remnants in the district were part of an extensive logging flume network and unrelated to mining (see Thybony and others, 1985, p. 65).
The Douglas Creek placer district has yielded small amounts of gold nearly every year since Moore's original discovery. Total gold production is inaccurately known, but is estimated at about 4,000 ounces for the pre-1965 mining operations in the district (Currey, 1965). Production of gold since 1965 has been minimal and probably totals less than a few hundred ounces.
Minor quantities of platinum and palladium flakes and nuggets (silver metallic, malleable metals with high specific gravity) have also been reported in some of the placers in the district. Scheelite (an important source of the strategic metal tungsten used to strengthen steel) has also been identified in the district in recent years. Scheelite is a milky white, fluorescent (light blue under short wave ultraviolet light) heavy mineral that is difficult to pan out of a gold pan.
Statistics on the size and weight of gold nuggets from the district are lacking, although the largest reported gold nugget was a 3.4 ounce nugget discovered prior to 1906. Every summer, a small amount of gold, including nuggets weighing generally less than 1 ounce, is recovered by hobbyists.
As you explore Douglas Creek, evidence of some of the 1930s to 1950s dredging operations can be seen. One of the more interesting areas includes the south side of Moores Gulch near the original gold discovery site where the remains of a small revolving bucket dragline are found. About a half mile south of Rob Roy Reservoir on Douglas Creek are some dredge tailings from a 1956 dredging operation (see Locality 48). Probably the best place to view some dredge tailings is at the Bobbie Thompson campground (Locality 52) south of Keystone. The unmined gravel adjacent to the tailings underlying the campground still contains gold. Another place to see dredge tailings is at the Pelton Creek campground (Locality 53).
Locality 50- Moores Gulch: This was named after Ira Moore who discovered gold here in 1868. Moores Gulch, including the area of Douglas Creek now under the Rob Roy Reservoir, became known as the Last Chance gold placers. During the first year of heavy prospecting (1869) as much as 400 ounces were recovered from this area (Hausel, 1989, p. 105).
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| The author looks at old gold placer dredge alone the edge of Moores Gulch gold placer. |
A small village known as Cinnabar City was sited at the mouth of Moores Gulch (Duncan, 1990). But when the Rob Roy Reservoir was constructed and filled with water from 1962 to 1965, this historic ghost town was submerged and lost forever.
In the 1980s, the reservoir was drained, dredged, and expanded. At that time, no effort was made to recover gold or platinum from the gravels and sediments (recovered from the historic placers) which were used to expand the dam. It has been said by more than one prospector that this dam might be "worth its weight in gold!"
Locality 51- Douglass City: In 1878, a town named Douglass City was built near the confluence of Douglas Creek with Little Beaver Creek to house many of the placer miners operating claims on Douglas Creek. The town had as many as 200 inhabitants in 1879 (Duncan, 1990). Only a few summer cabins remain of this once thriving village.
Locality 52- Bobbie Thompson campground: This Forest Service campground lies adjacent to Douglas Creek where extensive placer mining of the creek occurred sometime during the first half of the 20th century. Some of the dredged ponds presently provide good fishing holes.
Locality 53- Pelton Creek campground: There are more dredge tailings near the Pelton Creek campground. To get to these, drive about 8 miles northwest on Forest Service Road 898 (turnoff from State Highway 230 about 2 miles west of Mountain Home at the Colorado-Wyoming border). The tailings lie a short distance downstream from the campground on Douglas Creek. From the campground, follow the hiking trail north of the campground, cross the footbridge to the other side of Douglas Creek, and within a few hundred yards downstream are the old tailings from an early placer gold mining operation.
Locality 54- New Rambler district: West of the Rob Roy Reservoir and Douglas Creek is of one of the only mining districts in North America that recorded historical platinum and palladium production. In addition to these metals, copper, gold, and silver were also mined.
The New Rambler mining district lies on the northeastern edge of the Mullen Creek mafic complex, a highly deformed, 60 square mile, layered igneous complex similar to the Lake Owen complex to the southeast (Locality 63). The ore was localized in shear zones associated with altered rock. The principal rocks found in the area are amphibolite, granite, and biotite-plagioclase gneiss.
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| Prospect Mountain trench dug in the search for platinum- group metals. The MBM encloses some layered mafic complexes that are favorable hosts for platinum-group Metals. The author stands in the trench. |
Locality 55- New Rambler mine and Holmes ghost town: The New Rambler mine workings lie immediately south of Forest Service Road 500 just west of the Holmes campgound. Much of this land is privately owned rather than controlled by the U.S. Forest Service.
Shortly before the turn of the century, the New Rambler mine was developed as a gold prospect . But in 1900, copper was found at 65 feet below the surface. In the following year, platinum was detected in the copper ore, after 4,000 tons of the high grade copper ore had already been shipped to a smelter (McCallum and Orback, 1968).
The mine operated periodically from 1900 to 1918 until the mill and mine buildings were destroyed by fire. In total, the operation produced at least 6,000 tons of copper ore that also carried values in gold, silver, platinum, and palladium. Much of the ore was high grade concentrates from a supergene enriched zone at relatively shallow depths. At least 4,000 tons of this ore averaged 25 to 30 percent copper (McCallum and Orback, 1968). This would suggest a minimum of 2.0 to 2.4 million pounds of copper were recovered during the lifetime of the mine.
Available records of the U.S. Bureau of Mines (1942), suggest production from the New Rambler mine amounted to a minimum of 1.75 million pounds of copper with 7,350 ounces of silver, 170 ounces of gold, 170 ounces of platinum, and 450 ounces of palladium. In contrast, Silver Lake Resources, Inc. (1986) estimated platinum group metal production at 910 ounces of platinum and 16,870 ounces of palladium. This latter estimate probably includes platinum group metals assumed to have been lost at the smelter prior to their discovery in 1901. Additional work in this area in the last 50 years suggests there could be additional platinum ore in this region.
The platinum and palladium metals were found in covellite (iridescent blue to black metallic copper sulfide), pyrite, and in a very rare mineral known as sperrylite (silver gray, metallic, platinum arsenide). Sperrylite is found at only a few other localities in the world, and good specimens of the rare octahedron are nearly priceless.
Platinum and palladium are strategic metals used in the electonic, chemical, and medical industries, and are also used in jewelry. They are a necessary componet in catalytic converters used in automobiles to reduce emissions of carbon monoxide, hydrocarbons, and nitrogen oxides.
The New Rambler mine is situated in sheared (faulted) mafic and ultramafic rock at the northeastern edge of a layered mafic complex similar to the layered mafic igneous complexes in the Bushveld of South Africa and the Stillwater of Montana, where much of the world's platinum is currently mined. The complex hosting the New Rambler Mine is relatively small (60 square miles) and young (1.8 billion years old) when compared to the Bushveld (33,000 square miles), and the Stillwater (2.7 billion years old).
The ghost town of Holmes lies east of the New Rambler shaft. Prior to the spring of 1991, several decaying log cabins could be found in the forest east of the mine tailings.
Locality 56- Blanche mine: The Blanche shaft is located 600 to 700 yards west of the New Rambler mine, and lies in the forest along a dirt road running west from the New Rambler mine. The Blanche shaft was an exploration shaft developed to find the western extent of the New Rambler ore body. It was sunk to a depth of 160 feet, and at a depth of 120 feet the shaft penetrated a zone of low-grade copper mineralization.
The rocks encountered in the mine included gneiss, metagabbro, and metadiorite similar to those in the New Rambler mine. The mineralization occurred as milky quartz with bronze-colored, metallic pyrite; chalcopyrite; black, massive chalcocite; and bright green copper carbonate.
Locality 57- Lake Creek: This locality is about 5 miles northwest of Foxpark on Forest Service Road 512. The Lake Creek village on Lake Creek is a small community of summer cabins. A few old mines and prospects can be found in this area including the Lake Creek copper mine located at the apex of the hill north of the village.
Locality 58- Many Values pegmatite prospect: The Many Values prospect consists of two small prospect pits covered by decaying timbered headframes. This locality (E2 section 32, T13N, R78W) is about a mile west of State Highway 230 between Woods Landing and Mountain Home. The main pegmatite is exposed on the surface for 140 feet. This pegmatite contains abundant muscovite mica with quartz and feldspar. Other less common minerals include beryl (a beryllium oxide), garnet, small tantalite crystals, and some black tourmaline (schorl) (Osterwald and others, 1966, p. 132). In 1942 and 1943, some mica, beryl, and tantalite were mined from this prospect.
Locality 59- American copper mine: Not much is left of this mine located within walking distance of Forest Service Road 526 southeast of Mountain Home. The shaft has been filled and buried, but samples of copper-stained granite can still be found around the old workings. One sample of granite, stained with malachite and azurite (green and blue copper carbonates), collected from the mine site in recent years, assayed 1.4 percent copper and 3.0 ounces per ton of silver (Hausel and Jones, 1984).
Locality 60- Jelm Mountain mining district: The historic Jelm Mountain (Bramel) mining district lies in the foothills of the Medicine Bow Mountains along the Laramie River south of Woods Landing. Based on geology, the district is defined to run from Jelm Mountain and to continue westward across the Laramie River. The historic Old Jelm (Cummings City) townsite (Locality 61) lies on the west bank of the Laramie River, where the remains of the ghost town can be clearly seen from State Highway 10. Only minor amounts gold and copper were recovered from the district.
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| Rosasite from Jelm Mountain. This sample of the copper-zinc carbonate, was the first reported find of this mineral in Wyoming and found by the author. |
In 1872, the Bramel mining district was organized (Michalek, 1952). Gold was discovered in narrow, copper-stained, gossans hosted by amphibolite schist and gneiss. Small amounts of gold were also found in the placers of the Laramie River. All of the mineralized lodes were very narrow veins, shears, and rehealed faults.
Some exaggerated claims on the value of the lodes led to their promotion. In 1876, for example, a sample from the Sunrise mine on the southeastern flank of Jelm Mountain, was reported to assay 27 ounces of gold per ton with 950 ounces of silver per ton (Duncan, 1990). It is possible that a small, select, hand sample from the mine could have assayed relatively high in gold, but the silver content is highly improbable. Typically, these deposits have high gold to silver contents.
Interest in the district was further stimulated through grossly exaggerated claims made by two promoters, John Cummins and P.T. Smith. Duncan (1990) reported that in 1880, these two individuals claimed several samples from the district assayed from 1,780 to 3,480 ounces of gold per ton. In that same year, a local newspaper reported: "an expert who has visited Cummins City says the boom there is a fraud, and that the Mill Creek carbonates were brought from Leadville".
Undoubtedly, people were already questioning the exaggerated claims about the Bramel mining district. But, it should also be realized that it was not possible for this "expert" to have determined in 1880 the source of the ore without modern, detailed, geochemical analyses and techniques. Even with these modern techniques, it would be difficult to prove where the sample originated. It is also interesting that the newspaper story mentioned "carbonates", because the known Jelm Mountain deposits are primarily quartz veins and shears hosted by schist, granite, and gneiss, rather than carbonates.
In 1880, plans were drawn for the town of Cummins City along the Laramie River. In 1880, the town was described to have had 100 houses and a population of 300. Additionally, Cummins City was reported to have had 4 saloons, 5 stores, a library, three stamp mills, and a public meeting hall (Duncan, 1990). Conflicting reports claim the boomtown had a maximum of 30 buildings and a population that did not exceed 50. One of the structures that apparently did exist was a two story, 40 room hotel, which was later moved to Laramie sometime after the Jelm Mountain gold and copper booms (Wyoming Recreation Commission, 1976).
By the end of 1882, the gold boom was over, but Cummins City continued to survive as a stage stop (Duncan, 1990). In 1896, the district again came to life with more exaggerated claims of the size of Cummins City and the promotion of the copper found in the gold lodes. The Bramel mining district was also renamed the Jelm mining district.
But copper found in association with the gold occurred in tonnages too small to be commercially mined. There were reports of samples of ore assaying as high as 30 percent copper, but again such samples would have been spatially restricted. Without the development of any major mines in the district, Cummings City slowly disappeared.
Today, only about nine structures remain at the site of the historic boomtown (Figure 39). On the south side of Jelm Mountain along the observatory road (Locality 62), one can still see some of the historic mine workings. Samples of copper ore can be found on the dumps and in the lodes. The most common minerals are chalcopyrite (bronze-colored, copper-iron-sulfide), tenorite (jet black copper-oxide stain), chrysocolla (azure blue copper-silicate), and malachite (a green copper-carbonate stain).
Locality 61- Old Jelm (Cummins City) ghost town: see Locality 60 for discussion.
Locality 62- University of Wyoming's observatory: The Jelm Mountain observatory on top of Jelm Mountain is the home of the University's 92-inch infrared telescope. Tours of this facility can be arranged during the summer months through the University of Wyoming.
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| An old friend |
In recent years, 12 stratigraphic horizons in the Lake Owen complex have been identified with cumulate sulfide mineralization similar to the Stillwater complex in Montana, where the strategic metals platinum, palladium, and chromium are mined. Four of these horizons at Lake Owen have laterally persistent zones with anomalous concentrations of gold, platinum, and palladium that warrant further investigation. In addition to precious metals, significant chromite and persistent layers of vanadiferous magnetite-ilmenite occur in the Lake Owen complex (Loucks, 1991). The vanadiferous magnetite-ilmenite layers are considered as potential sources of the strategic metals vanadium and titanium, and also have significant amounts of iron and some copper (R.R. Loucks, personal communication, 1991).
Locality 64- The Little Laramie oil field: A short distance west of Interstate 80 at the Herrick Lane overpass is the Little Laramie oil field in the flood plain of the Little Laramie River. This field was discovered in 1948 by Superior Oil Company. The oil is produced from the Casper Formation at a depth of 3,700 feet below the surface (Hausel and Jones, 1984).
Locality 65- Quealy Dome oil field: In the foreground south of Interstate 80, is the Quealy Dome field. Oil was discovered here in 1934 and is recovered from the Muddy Sandstone and sandstones in the "Dakota" (Cloverly), Sundance, and Casper Formations (Hausel and Jones, 1984).
Locality 66- Cooper Hill district: The Cooper Hill district lies south of Interstate 80 along the northeastern slope of the Medicine Bow Mountains and includes a bald (treeless) hill known as Cooper Hill easily seen from Interstate 80. Access to the district is privately controlled and permission is required from the surface owners.
Gold, silver, lead, and copper lodes were discovered in this area following the discovery of mineralized float along Cooper Creek in 1893 (Schoen, 1953). This district was originally included in the Herman mining district (Duncan, 1990), but currently is known as the Cooper Hill district.
From 1893 until 1897, several mines recovered some ore in the district. In 1896, the town of Morganville (later changed to Morgan) was laid out at the southern end of Cooper Hill and included a saloon, hotel and several cabins (Duncan, 1990). In 1897, according to Duncan (1990), a 10-stamp mill was built to process ore stockpiled from the previous years, but recovery of metals from the mill was much less than anticipated and the district soon was deserted. Unfortunately, stamp mills were designed to extract easily recoverable gold with some silver. The ore from Cooper Hill included lead, silver, copper, and antimony in addition to gold (Schoen, 1953). Thus many of these valuable metals were probably lost to the tailings.
Investigations by the author identified copper-bearing skarns, silver- and lead- replacement deposits, and some veins. The skarns are formed of minor amounts of pyrite, chalcocite, and chalcopyrite in epidote-chlorite-magnetite-actinolite-garnet-calcite hornfels and represent altered limestones. The silver- and lead- replacement deposits contain argentiferous (silver-bearing) galena, polybasite, common pyrite, and gold and also occur in altered limestones.
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| Gold with pyrope garnet found in Douglas Creek |
In 1991 and 1992, several sites along Cooper Creek were sampled and panned for gold. Nearly every sample collected in this area yielded anomalous concentrations of gold and visible gold colors. Even a sample panned from the sand and gravel in Cooper Creek adjacent to Interstate 80 produced some visible gold (Hausel and others, 1992).
Guide to the mining districts of the Medicine Bow Mountains
In the past, the Medicine Bow Mountains supported several mining operations in which copper, gold, silver, platinum, palladium, and rare earths were recovered. And as recently as 1977, diamonds were found in the northern Medicine Bow Mountains by a gold prospector (Paul Boden) from Saratoga, Wyoming. Although none were very large, the placer operations of the Douglas Creek district were widespread and recovered moderate amounts of gold with some platinum. Other important metal production came from lodes such as the Keystone, New Rambler, and Centennial mines.
At the time of the writing of this guide, no mines were operating in the Medicine Bow Mountains, and only a few hobbyists and part-time prospectors with small hobby-type dredges were recovering some gold and platinum from the creeks during the summer months.
The geology of the Medicine Bow Mountains suggests that there is a possibility for large undiscovered mineral deposits. For example, in the northern Medicine Bow Mountains there are thick successions of quartzites with radioactive quartz pebble conglomerates which have many characteristics of the uranium-rich Blind River deposits of Canada, and the gold- and uranium-rich Witwatersrand deposits of South Africa. These similarities could be very significant, particularly when one realizes that 52% all the gold mined in human history has been mined from the Witwatersrand conglomerates of South Africa.
In the central and east-central parts of the Medicine Bow Mountains are two large layered mafic complexes similar to both the Bushveld Complex in South Africa and the Stillwater Complex in Montana. These latter two complexes host most of the world's known reserves of platinum, palladium, osmium ruthenium, iridium, and rhodium as well as significant amounts of chromium, vanadium, and gold. Thus, based on geological similarities, the Medicine Bow Mountains could contain valuable mineral resources of a number of important scarce strategic metals as well as precious metals. Dedicated to those WGS geologists who gave their lives - Ray Harris, Bob Lyman, and Richard Jones.
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