Saturday, August 21, 2010

THE FERRIS-HAGGARTY COPPER-GOLD MINE, GRAND ENCAMPMENT DISTRICT, WYOMING

At the close of the 19th Century, optimism was high that Wyoming would become an important source for copper much like the neighbor states of Colorado, Utah, and Montana. This dream was short-lived when the Ferris-Haggarty mine in the Grand Encampment district became one of the 30 most important copper mines in the world during the first decade of the 1900s. But due to a series of disasters at the Boston-Wyoming mill and smelter complex at Riverside, the Ferris-Haggarty mine permanently closed in 1908 as a result of financial problems. Wyoming never again gained stature as an important copper-producing state even though several large copper-silver porphyry deposits similar to those in Montana and Utah, were found at the opposite end of the state immediately east of Yellowstone National Park in the Absaroka Mountains. These properties included Kirwin, Bald Mountain, Stinkingwater, Sunlight and several others and the likelihood of  dozens of similar deposits in this region is very favorable. But Yellowstone and the Absaroka Mountains were withdrawn by National Park, Wilderness, wilderness study, primitive area and other designations that locked up an area as largs as some states.

LOCATION
The Ferris-Haggarty mine is located within the Grand Encampment district of the Sierra Madre Mountains. The Sierra Madre are a forest covered mountain range that rise from the valley floors of the adjacent Great Divide and Platte River Valley basins to over 10,700 feet at Bridger Peak in the heart of the range. Nearby towns include Encampment, Saratoga, Baggs, Sinclair and Rawlins. The district is known for hundreds of historic mines and prospect pits that were dug to test for copper, nickel, cobalt, platinum, palladium, zinc, lead, tantalum, rare earth metals, garnet and/or gold. The district recently was of interest for platinum-group metals and nickel following discovery of anomalous nickel, palladium, gold, copper, silver and platinum (Hausel, 1995, 1997). and typically attracts hundreds of prospectors and treasure hunters each year to search for gold and diamonds.

HISTORY
The first known mining claims in the region were staked in 1868. Six years later, a significant copper discovery was made when copper-stained float was found near the continental divide close to Battle Lake. This discovery led to the development of the Doane-Rambler copper mine in 1881, and the small mining community of Rambler was built adjacent to the mine. Following the discovery, the Sierra Madre Mountains attracted hundreds of prospectors in the search for copper and gold.


Ore specimen from the Ferris-Haggarty ore shoot. One of the great mysteries
about the F-H mine was the type of ore since the mine had been inaccessible
for nearly a hundred years; yet this was one of the greatest copper mines in
the world in the 19th century.

Investigations by Exxon Minerals in the 1980s
identified a sizable gold anomaly at the mine, but the deposit remained
basically unexplored along trend and depth (and still does). This specimen
suggests considerable brecciation of the ore and replacement of the matrix with
massive copper. The deposit lies in the middle of Proterozoic schists deposited
near an island arc possibly 1.6 billion years ago, and is in the middle of a
known massive sulfide district due to initial research by Conoco
Minerals in the late 1970s. Some volcanogenic massive sulfide deposits
mined in Canada and in Arizona have produced $billions in metals. It is
likely that the Ferris-Haggarty still contains sizable ore resources and the
surrounding region contains several economic massive sulfides - however,
during the 1980s, the US Forest Service piecemeal withdrew land following
every discovery of a massive sulfide deposit in the Sierra Madre Mountains
of Wyoming essentially nationalizing our natural resources.
For the people who still enjoy working, if the FS would support these kinds of
projects instead of withdrawing the land, Wyomingites and Coloradoites could
have hundreds of high-paying mining jobs if any of these massive sulfides were
developed.
Evidence of the intense prospecting can still be seen from many prospect pits and abandoned mines scattered all over the mountain range; although, many of these are no longer as visible as they once were due to wasteful expenditures related to government-funded reclamation projects.


By 1901, it was estimated that 2,500 prospect holes were dug, several thousand mining claims were staked, and 260 mining companies were operating within the district. Several years following the Doane-Rambler discovery, another significant copper discovery was made in 1897 northwest of the Doane-Rambler mine. Like the Doane-Rambler discovery, copper at this latter discovery was also hosted by quartzite. In the following year, an adit was dug to test this gossan and massive copper was intersected within 39 feet. The ore was incredibly rich, and the first 14-ton shipment averaged 33.18% copper! At this time in history, copper was selling for $0.16 to 0.18/pound and silver was selling for $0.60/ounce. The intersection of incredibly rich ore ultimately led to the development of the greatest copper mine in Wyoming. According to Houston (1992), this was one of the more important copper mines in the West at this time in history, and the mine was ranked as the 27th largest copper producer in the world in the early 1900s (Short, 1958), although the mine would have a relatively short-lived history.


Historical photo of the Ferris Haggarty mine with Tram
Following discovery, the region experienced a mining boom and the town of Encampment along the eastern flank of the Sierra Madre blossomed. Other towns were established including Battle, Copperton, Dillon, Elwood, Rambler, and Riverside. To support the development of the Ferris-Haggarty mine, construction on a 16.25-mile-long tramway began at the mine portal on Haggarty Creek along the western flank of the Sierra Madre range at an elevation of 9,880 feet. From the mine, the tramway ran up the western slope crossing the continental divide at 10,690 feet, and continued down the eastern slope of the range terminating at the Boston-Wyoming mill and smelter at Riverside along the Encampment River at an elevation of 7,200 feet. Both the tramway and smelter were completed in 1902. The tramway was an enormous engineering undertaking and included 304 wooden towers, which supported 985 ore buckets. Each bucket was rated at 700 to 1,000 pounds carrying capacity (Beeler, 1905; Vandenberge, 1906). The structure was the longest aerial tramway in the world at that time (Short, 1958).


The tramway terminal was at the Boston-Wyoming mill and smelter complex that was constructed along the Encampment River at Riverside. This complex had a maximum operating capacity of 500 tons per day (Armstrong, 1970).


GRAND ENCAMPMENT DISTRICT
The Grand Encampment district was organized in the late 19th century. According to some descriptions, this district originally encompassed much of the Sierra Madre as well as a large part of the adjacent Medicine Bow Mountains to the east. Several smaller districts were included within the parent district such as Battle, Encampment, Purgatory Gulch, Sandstone, New Rambler, Keystone and others.


Historical records from the early 1900s indicate that the Ferris-Haggarty mine was the largest copper producer in the district, followed by the Kurtz-Chatterton, Doane-Rambler, Charter Oak, and at the time, 53 other mines with dozens of other properties in the initial prospect stage (Armstrong, 1970). Many of the deposits yielded rich ore from surface gossans (rusty appearing rock), but only in a few cases did the rich ore continue at depth. Beeler (1905) reported shipping ore from some of the mines often yielded 35% to 49% copper in carload lots. The gold and silver values were uniformly low, although some rich gold samples were found in the oxidized ores at Purgatory Gulch, the Charter Oak mine, and others. During reconnaissance in this region, the author identified several gold deposits of potential interest along with the anomalous mineralization at Puzzler Hill. Anomalous platinum, palladium, and nickel were found on a few properties, and one mine (New Rambler), became one of the only commercial palladium-copper (with associated values in platinum, gold, and silver) mines in North America in the historic past.


Ore from the Ferris-Haggarty mine consisted of mixed chalcocite and bornite, and shipments often yielded more than 35% Cu. By 1900, the Ferris-Haggarty mine was averaging about 550,000 pounds of copper per month (Hausel, 1993).

 
Geology
The Grand Encampment district is divisible into a northern and a southern region based on geology. These two regions are separated by a major east-west-trending structure known as the Mullen Creek-Nash Fork shear zone (Houston, 1993). The shear zone is host to several gold, copper, and some platinum group metal deposits in the Sierra Madre and nearby Medicine Bow Mountains. The shear can be visualized as a zone of intensely deformed rock that is as much as a mile wide in some places, and is thought to represent a fossilized subduction zone, where an oceanic basin to the south was subducted under an ancient continent to the north about 2 billion years ago.

North of the shear , the rocks are primarily 2 to 2.5 billion year old metamorphosed conglomerates, limestones, sandstones, shales, and some volcanics. Such rocks would be expected to occur along the edge of an ancient continent. The principal mineral deposits found in these rocks include uranium- and thorium-bearing conglomerates that locally contain some gold and diamond, gold-bearing quartz veins, copper-bearing quartzite, and modern gold placers. The Ferris-Haggarty mine is located within this terrain.

To the south, rocks are younger and different. These include 1.6 to 1.9 billion year old metamorphosed volcanic rocks (basalts, andesites, rhyolites, tuffs), and volcanic-derived sediments believed to have been deposited in an ancient sea and on volcanic islands. This region also includes some large, circular, layered gabbroic (dark, coarse-grained basaltic rock) complexes that are host to several significant platinum, palladium, chromium, vanadium, and titanium occurrences and anomalies. Other mineral resources include copper- and gold-bearing veins, copper-bearing shear zones, and copper-zinc-bearing massive sulfides and zinc-lead-copper skarns. The northern and southern regions, as well as the shear zone itself, are also considered to have high potential for the discovery of diamond deposits.



Ferris-Haggerty mine
In 1897, a prospector by the name of Ed Haggarty discovered a cupriferous gossan (copper-stained rusty rock) along a drainage that would later bare his name (Haggarty Creek). A shaft (known as the Rudefeha shaft) was sunk in the gossan and intersected massive bornite (copper-iron-sulfide) at 39 feet. Shortly after the massive copper was intersected, the property was sold to the Penn-Wyoming Copper Company and capitalized for $20 million.


The ore was described to occur in a fold along a contact between quartzite and schist. The ore zone averaged 20-feet-thick and occurred in brecciated footwall (underlying) quartzite (Spencer, 1904). Locally, the production zone was as much as 65 feet thick, and averaged 6 to 8% copper (many of the larger copper mines today, produce ore that typically averages less than 1% copper). High-grade ore mined from the shoot supplied the Boston-Wyoming smelter at Riverside with 200 to 500 tons of ore per day. Some of the high-grade ore yielded 30 to 40% Cu with some silver and 0.1 to 0.4 opt Au. The ore was mined from a zone that was at least 250 to 300 feet long and was developed to a depth of 300 feet in 1903. The workings may have ultimately extended to a vertical depth of 560 feet prior to termination of the mine operations in 1908.


The principal ore minerals were copper sulfides known as chalcocite and chalcopyrite with minor bornite and covellite (Hausel, 2009). Other minerals found on the mine dump include cuprite (copper oxide), pyrite (iron sulfide), malachite (copper carbonate), and chrysocolla (copper silicate). Records indicate that the mine may have produced 21 million pounds of copper with some gold and silver. The amount of ore remaining in the mine is unknown, but could be significant. For example, large unmined blocks and pillars of rock were mapped in the mine during the second world war that contained an average of 5% copper (Ralph Platt, personal communication, 1985). In addition, a sampling program completed in some of the accessible upper workings of the mine by Exxon Minerals in 1988 yielded rock that assayed from 0.1 to 21.3% Cu, 1.1 ppm to 2.34 opt Ag, and 75 ppb to 0.33 opt Au. Resources in this part of the mine were estimated at 928,500 tons of ore averaging 6.5% Cu containing 116,800 ounces of gold. Based on value, the Ferris-Haggarty mine could be considered a gold mine with value-added copper and silver. It should be noted that the rest of the mine remains unexplored in modern times, and the possibility of similar ore deposits in the region is likely!


It is interesting that the ore was described to occur as fault breccia in quartzite along a contact with schist (Spencer, 1904). Examination of the ore zone by the author showed that it was indeed brecciated and deformed in a shear zone, but that undeformed samples of the ore showed that the copper occurred in conglomerate and possibly millrock. The matrix of this metamorphosed conglomerate (metaconglomerate) consists of massive copper ore supporting rounded pebbles and cobbles. This rock appears to represent an ancient copper placer. When copper was deposited about 2 or more billion years ago, the earth’s atmosphere did not have enough oxygen to oxidize copper. Thus the copper was carried downstream in an ancient river, much like gold is today. After the earth’s atmosphere later became sufficiently oxidizing, it was no longer possible to produce copper placers, since copper is easily oxidized and transported in solution in water, rather than as massive ore.


Because of the Ferris-Haggarty mine, the economy of the region boomed for nearly a decade, but then problems began in 1906. In 1906, a portion of the mill at Riverside was destroyed by fire. The damaged mill was reconstructed, but in the following year (1907), a large segment of the mill and smelter complex were destroyed by fire.


These disasters were followed by a 35% decline in the price of copper. The price drop, along with the fire damage was more than the Boston-Wyoming Mining Company could handle. The mine permanently closed in 1908 and more than 200 miners were laid off. With the layoff, the towns of Encampment and Riverside became economically depressed and never totally recovered.


REFERENCES CITED
Armstrong, J.R., 1970, Grand Encampment 1898-1912: High Country Treasure: Rawlins Newspaper, Inc., Rawlins, Wyoming, 19 p.


Beeler, H.C., 1905, Mining in the Grand Encampment copper district, Carbon and Albany counties, Wyoming (2nd edition): Office of the State Geologist, Cheyenne, Wyoming, 31 p.


Hausel, W.D., 1986, Mineral deposits of the Encampment mining district, Sierra Madre, Colorado-Wyoming: Geological Survey of Wyoming Report of Investigations 37, 31 p.


Hausel, W.D., 1993, Mining history and geology of some of Wyoming's metal and gemstone districts and deposits: Wyoming Geological Association Jubilee Field Conference Guidebook, p. 39-63.


Hausel, W.D., 1995, Reconnaissance of the Charter Oak mine and Cu-Ni-Au-Ag-Pt-Pd mineralization associated with the Puzzler Hill layered mafic-ultramafic complex, Encampment district, Sierra Madre, Wyoming: Wyoming State Geological Survey, Mineral Report MR95-2, 11 p.


Hausel, W.D., 1997, The Geology of Wyoming's Copper, Lead, Zinc, Molybdenum and Associated Metal Deposits: Geological Survey of Wyoming Bulletin 70, 224 p.


Hausel, W.D., 2009, Gems, Minerals and Rocks of Wyoming. A Guide for Rock Hounds, Prospectors & Collectors. Booksurge, 175 p.


Houston, R.S., 1992, Proterozoic mineral deposits near plate margins of the Archean Wyoming Province, USA: Precambrian Research 58 p. 85-97.


Houston, R.S., 1993, Late Archean and Early Proterozoic geology of southeastern Wyoming in Snoke, A.W., Steidtmann, J.R., and Roberts, S.M., eds, Geology of Wyoming: Geological Survey of Wyoming Memoir 5, p. 78-116.


Short, B.L., 1958, A geologic and petrographic study of the Ferris-Haggarty mining area, Carbon County, Wyoming: M.A. thesis, University of Wyoming, Laramie, 100 p.


Spencer, A.C., 1904, Copper deposits of the Encampment district, Wyoming: U.S. Geological Survey Professional Paper 25, 107 p.


Vanderberge, J.H., 1906, An independent engineer's report on the properties of the Penn-Wyoming copper company and the Grand Encampment mining district: Geological Survey of Wyoming Mineral Report MR06-1, 25 p.





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