The Eagle's Nest mine Placer County California.
Specimens of crystallized gold from what is now known as the Eagle's Nest mine first came to the attention of the mineral collecting community in a brief article in the Mineralogical Record's, "What's New in Minerals" column (Leicht, 1982). At that time, specimens were simply labeled as coming from the Michigan Bluff Mining District in Placer County. Since that time, substantial numbers of beautiful gold specimens have reached the market. The present owner/operator has purchased and leased other claims in the immediate area and has consolidated them under one name: the "Eagle's Nest mine." Consolidation of many claims under one name is not unprecedented in California. The 16 to 1 mine in Sierra County, the Red Ledge mine in Nevada County (8 claims), and the Sonora mine in Tuolumne County all encompass numerous claims.
Historically most of the mining in Placer County has been placer, both from recent stream deposits as well as from old Tertiary channels which bisect the County. Placer and drift mines (a "drift mine" is an underground mine exploiting ancient river gravel) were particularly rich and were mined intermittently since the early 1850's. Lode mining in the Michigan Bluff District began shortly after the discovery of gold in California but was never as important as the alluvial deposits. The site of the original discovery of gold at Coloma in El Dorado County is less than 20 miles from the Eagle's Nest mine. One of the earliest reports of lode mining near Foresthill can be found in the American Journal of Science and Arts, written by William F. Blake (1855); he states that "... interesting octahedral crystals have been found in the claims of the Messrs. Diedesheimer ... 2,500 feet above the level of the river." From his description it appears that these crystals of gold must have been found in either the Michigan Bluff District or the adjacent Foresthill District.
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During the California gold rush, Michigan Bluff was a booming town of several thousand citizens. It was originally settled by immigrants from the State of Michigan and was simply called "Michigan" until the town was physically moved to a higher bluff when gold was discovered beneath the townsite. It is now better known as the town where Leland Stanford started his career as a lowly store merchant in 1853. He became part of the "Big Four," which included C. Crocker, C. P. Huntington and M. Hopkins, and together they financed the Central Pacific Railroad. Later he became Governor of California and founded Stanford University.
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Early lode mining in the County was obviously overshadowed by the extensive placer, drift, and hydraulic mining in the area. There were never any rich deep mines like those in Mariposa, Tuolumne, Calaveras, Nevada, Sierra, or even the tiny County of Amador. Almost all the lode mines in the Michigan Bluff District were small "pocket" mines where the gold was found in narrow stringers near the surface. Often pocket mines do not produce enough gold to be commercially profitable from the sale of bullion alone, but if the gold is crystallized it can be sold at several times its bullion value to collectors. Other pocket mines in the Michigan Bluff District include Ford's mine (inactive) and the Golden Sheaf mine (mined briefly at the turn of the century). In the past, Placer County has been the source of some of the finest crystallized gold ever found in California, from mines on both sides of the Foresthill Divide which bisects the County, separating the North and Middle forks of the American River. The famous Golden Bear Nugget was thought to have been found at the George Hill mine near the town of Yankee Jim's, Placer County, some 10 miles from the town of Foresthill (Bradley, 1922). Some of the claims which make up the Eagle's Nest mine were located shortly after the turn of the century and in the early literature were referred to as the Garbe and deMaria mine (correctly written as DeMaria). At that time the mine was operated by Mr. Louis Garbe and Mr. Clement DeMaria, as partners. Around 1921, Mr. John (Jack) Greenwood joined the mining venture. Jack Greenwood was a relative of Louis Garbe and also of the family after which the town of Greenwood in El Dorado County is named. He is also the grandfather of the present owner's late wife. Jack Greenwood had a long history of successfully operating gold mines in both El Dorado and Placer Counties. When Jack was associated with the mine several large pockets of gold were found.
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After Clement's death, his son, John R. DeMaria, assumed the family's interest in the mine. Records of production during this period are sketchy, but the Thirty Second Report of the State Mineralogist, published in 1936, states that for "many years this mine has been noted for occasional 'pockets' of coarse crystallized gold." It also states that the present operators (presumably John R.) "professed to be at a loss to recognize any sure sign of 'pay.'" Obviously John R. was not the miner his father was; his wife stated that during the period from 1938 until he ceased active mining operations he found only "colors" (traces of gold)! She later stated that her husband had personally mined less than one ounce of gold on their claims in 40 years! Obviously the DeMaria family relied upon others to do their mining and were content to collect royalties from their claims.
Just before the State Mineralogist's Report of 1936 was published, Charles "Bud" Greenwood, Jack Greenwood's son, and father of the present mine owner's wife, joined John R. in the mining operation. Bud, like his father, Jack, was a hard-working, industrious miner who learned how to read the signs of pocket mining from his father. When Bud was associated with the claims owned by the DeMaria family, again, many fine specimens were found. He also located two additional claims, the Hope and the Wildcat, and worked them independently of the DeMaria operation. The DeMaria family had no financial interest in these claims. Many of the largest gold specimens found in the district came from the Hope claim during the period from 1900 to 1939, at which time Bud left for military service. Specimens on display at the Placer County Courthouse in Auburn, California, came from the Hope Claim and were sold to the county in the early 1920's by Louis Garbe. The Hope claim is often referred to as the Frenchman's Adit, in reference to a Frenchman named "Frenchy" LaBarr who illegally worked the claim in the late 1920's and early 1930's. Even though the adits for the various claims are separated by some distance, recent geological studies indicated that all of the claims are in the same geological setting with the gold deposited in the same mineralogical event. There is some indication that the Hope and the Wild Cat are potentially richer than the five DeMaria family claims. The mine owner has, in the past, concentrated his efforts on the DeMaria family claims and has left the Hope and Wildcat for development at a later date. However, several large specimens have been found on these claims recently, through the use of advanced metal detectors capable of detecting gold at greater depth than earlier models could.
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During the war years very little development, apart from the required assessment work, was done by John R. on his claims. Shortly after Greenwood's discharge from the military in 1945, he was stricken with polio and retired from any mining activity. Bud's previous work on the Hope and Wildcat produced several large plates of quartz containing large amounts of gold. These were passed on to Bud's daughter, Denise, after Bud's death in 1984. When one of us (WCL) asked Bud in 1982, shortly before he passed away, why he saved these pieces he simply stated that he did not know how to prepare them properly for market even though he believed they contained several ounces of crystallized gold. One specimen, which was as large as a dinner plate, he estimated to contain only 10 ounces of gold, but it actually contained much more! This specimen was prepared and sold, and the money was used to help finance future development of the mine. Bud further indicated that most of the gold he mined was sold for little more than bullion value, but he always believed that the price of gold would go up in the future and the specimens he saved would increase in value.
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In 1965 Bud's son-in-law, the present mine operator, became involved in the mining operation. Although confined to a wheelchair, Bud taught his son-in-law the telltale signs for finding gold in pocket mines, even though neither had any formal training in geology or mining. At that time, apart from keeping up the assessment work on their claims, the DeMaria's were not actively mining on their claims. John R. undoubtedly felt that his claims were "played out" and decided to lease two of his claims to Bud's son-in-law.
Presently the Eagle's Nest mine consists of over seven unpatented claims of approximately 20 acres each, located approximately 4 miles from the small town of Foresthill in Placer County, California. Five of the claims, the Big Seam, the Red Ink Maid, the Dandy, the Louise and the Moonshine, are contiguous claims. Two other claims, the Hope and the Wild Cat, are located northwest of the main portal and across a county road. Other lode and placer claims in the area have also been located by the mine owner but are not being worked at the present time.
The Eagle's Nest mine was initially developed by a series of short adits that accessed somewhat chaotic workings along the narrow, gently dipping quartz veins. Today, however, a much better planned and developed mine exists that exploits what are referred to as the 300, 350, 400 and 500 veins. Older, upper workings that do not connect with the current operations are on what are designated as the 100 and 200 levels. The deeper levels are accessed by inclines from the 350 level, with the deepest current workings on the 400 vein; the 500 vein area is currently temporarily flooded. Ventilation and emergency exits are provided by drifts to the surface from the main 300 and 400 vein workings, and there are several equipment/supply raises and winces. In total, the workings encompass several thousand linear feet, underlying a surprisingly small area that is about 400 X 250 feet exclusive of the main adit and the ventilation shaft.
Stopes are open rooms that vary from about 6 to 10 feet in height, generally opened with the quartz vein on the floor. Pillars are left at somewhat random intervals and supply the only needed support in the mine. Blast holes are drilled with a small compressed-air jackhammer and all rock loading and haulage is carried out with a rubber-tired scoop tram. Mining is carefully controlled and quite selective; pockets are located with the aid of metal detectors and are then worked out by hand. There is no operative mill at the mine, and gold-bearing, non-specimen-grade ore is carried off site for processing. A guard animal patrols the mine at night and during periods of inactivity.
The mine is located within the complex Foothills Metamorphic Belt at a position approximately 15 kilometers upstroke (north) of the generally accepted terminus of the great Mother Lode Belt (Ransome, 1900; Logan, 1935). The geology of the Mother Lode proper, as well as similar outlying districts, such as Grass Valley and Allegheny, for example, have been discussed at depth in the technical literature for over a century (Lindgren, 1895; Knopf, 1929; Johnston, 1944; Ferguson and Gannett, 1932).
The Foresthill and Michigan Bluff districts have been described by Chandra (1961), who gives the only relatively detailed, modern account of the mine area geology in his description of the Colfax and Foresthill quadrangles.
The Foothills Metamorphic Belt is composed of a series of multiply deformed, accreted blocks. In the mine area, the rocks comprising the host block are moderately metamorphosed Upper Paleozoic sediments and intercalated volcanic rocks of the Calaveras Group that are locally cut by dikes and multigenerational quartz veins. A complex mass of Upper Jurassic serpentinite lies north and west of the metasedimentary-metavolcanic mine-area sequence and is separated from it by the Volcano Canyon thrust fault. Tertiary flows and tuffs crop out approximately 2 km northeast of the mine, obscuring the gold-bearing sequence.
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Rock units within the immediate mine area most likely correlate with the Blue Canyon Formation and consist of variably graphitic and pyritic slate, metaconglomerate, gritty quartzite, and metagray-wacke. Minor amounts of the Tightner Formation have also been mapped near the mine and consist of distinctive intermediate to mafic metavolcanics including amphibolite and amphibole schist. The thickness of individual units or "beds" is quite variable and progressive changes in unit thickness within the mine suggest the presence of one or more isoclinal folds. Steeply dipping, variably altered lamprophyre dikes up to 1.5 meters thick cut units of both formations and are obvious throughout the mine workings. Dominant east-west-striking and north-south-striking dikes intersect within the mine and have been used for location reference on all levels. Petrographic and geochemical examinations of major rock unit samples collected from within the mine indicate that alteration includes silicification of dramatically variable intensity and pervasive though generally less intense carbonate alteration proximal to quartz veins. Local bands of mylonitic recrystallization are common, particularly near boundaries between units of differing competencies. All major rock units, with the exception of dikes, are foliated at some scale, although the more equigranular grits retain a somewhat massive bedded appearance in outcrop. Foliations most commonly strike steeply to the north and exhibit a variable though typically steep dip. Graded bedding is locally preserved.
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The structural setting is somewhat complex. The Blue Canyon and Tightner formations are folded together into relatively tight north-northeast-trending, northwest-vergent antiforms and synforms. Chandra (1961) has mapped a dominant open, northeast-plunging antiform across the southeast portion of the claim block, implying that the majority of the mine workings lie within its west limb. East of this fold, a north-striking, very steeply dipping fault of unknown displacement has carried rocks of the Blue Canyon Formation west of the fault upward against what is interpreted to be a structurally higher part of the Blue Canyon-Tightner stratigraphy. Within the mine proper, the productive workings appear to terminate to the west against a fault of unknown displacement. Elsewhere, very minor normal and reverse displacement is exhibited along widely spaced faults that appear to represent joints along which sporadic local movement has taken place.
Gold occurs within small, very irregularly distributed zones in a set of narrow, subparallel, gently dipping quartz veins. This vein set typically strikes north-northwesterly and dips gently to the northeast. At least four productive veins, separated from each other by several tens of meters, have been identified, along with numerous similar though barren veins. Veins are typically quite thin, averaging about 5 cm in thickness. Although they are generally persistent throughout the workings, they can be seen to pinch and swell locally and in some places have thinned to the point of disappearing completely. Although gone, their traces are marked by joint-like seams which continue on in structural continuity and which gradually become quartz-filled again down dip or along strike. Joints that contain no quartz veins but are subparallel with those serving as the locus of auriferous veins are common throughout the mine.
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The specimen-gold-bearing veins are generally featureless and massive, although ankerite occurs locally, intergrown with quartz near vein margins; thin seams of carbonate locally mark vein walls. Small quartz-crystal-lined pockets have been encountered, but only rarely, and these are typically barren of other minerals. The productive (auriferous) quartz veins are surprisingly free of sulfide minerals, and the system as a whole is generally sulfur-poor, the highest sulfur content being within pyrite-bearing lamprophyre dikes, where it reaches almost 3%. Trace metal analyses of veins and immediately adjacent wall rock reflect low Cu, Pb, Zn, Te, Sb and As contents.
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The host rocks are also cut by generally steeply dipping veins and lenses of quartz of an apparently different generation from that which produced the specimen-bearing veins. Many of these appear to be sweat-outs contemporaneous with peak regional metamorphism. Pyrite is locally associated although its gold content is almost invariably low, and these veins have not produced gold specimens.
By far the most common habit of crystallized gold from the Eagle's Nest mine is flattened octahedrons which commonly extend into thin dendritic plates. Solid plates with sharp edges are less common. Recently several specimens were found on the Hope claim which are in the form of solid plates. Well-formed equant octahedrons are found only rarely. Almost always they exhibit some degree of "hoppered" growth, especially in the larger crystals. Only one or two wires have been found in the over 20 years of my association with the Eagle's Nest mine.
The composition of the gold from all of the claims is remarkably consistent in terms of the fineness and trace element profiles, suggesting that the gold was deposited during the same mineralogical event. The fineness is almost always between 870 and 880, with silver being the dominant impurity.
Eagle's Nest mine gold specimens are particularly easy to prepare. The gold usually lies within narrow seams of quartz which are generally 1 to 2.5 cm thick. No sulfides or tellurides are associated with the gold. The area where the gold is best crystallized is usually obvious because the quartz tends to be brecciated in that area, or is associated with carbonate-rich rock. In cases where it is not obvious where quartz needs to be removed, an X-ray of the specimen might be required. Based on the X-ray I can decide where quartz needs to be removed and where the quartz should be retained to form a natural base. I experimented with several X-ray techniques, one of which (though expensive) proved to give the best results; that technique remains proprietary and will not be described here. However, readers thinking that perhaps they can run to the nearest doctor's office for a quick X-ray of a specimen will be disappointed. Medical X-ray equipment will not do the job!
From the X-ray photograph I can usually tell how well the gold is crystallized and whether it will "hold together" during preparation. The only difficulty occurs when the gold lies in more than one layer, one on top of the other. The X-ray shows only the shadow of all superimposed layers on the film plane, and side-view X-rays are even more difficult to take and interpret.
Normally the removal of quartz requires the use of hydrofluoric acid (HF) but more recently I have been using only mechanical vibrating tools with carbide tips to spall the brittle quartz from the more ductile gold. This is especially true of specimens which I plan to market in Europe. Europeans are often adverse to acid-etching of gold specimens, even though they may already own benitoites, silvers and other specimens which have been etched from the matrix. The rules seem to change when it comes to gold!
The outlook for continued production from the Eagle's Nest mine seems promising. The current owner/operator of the mine along with his two sons have become accomplished miners and seem to be able to "read the signs" of a pocket mine even better than their grandfather and great grandfather. Currently mining is concentrated on the two claims partially owned and leased, with plans for further development on the Hope and Wildcat at a later date. However, several significant specimens have been found on these claims using recent improvements in metal detectors, even though the old workings can only be worked with a wheelbarrow and hand tools. In the future the Hope and the Wildcat will likely provide some of the best specimens from the claims which make up the Eagle's Nest mine.
The energy, passion and commitment of the current operators of the mine are inspiring. A man, his wife and his two sons and their young families have been through the best of times and the worst of times. The recent death of the miner's wife has left all of us who know this family deeply saddened.
Thanks are also due Harold and Erica Van Pelt and Jeff Scovil for their unique talents in photography. And thanks to special friends like Dick Thomssen, Bob Jones, Bill and Roberta McCarty, Richard Bideaux and to all of our supporters. And a special thanks is owed to Stephanie Andrews for always "being there" when needed.
And yes, there is indeed a woman behind the man [WCL]: my wife of 39 years, Dona, has been a willing partner through ups and downs of a somewhat crazy business.
BLAKE, W. P. (1855) Observations on the extent of the gold regions of California and Oregon ... and some remarkable specimens of crystallized gold. The American Journal of Science and Arts, 58, 72-80.
BRADLEY, W. W. (1922) California mineral exhibit during the Shrine Convention. Annual Report of the State Mineralogist, p. 275-277.
CHANDRA, D. K. (1961) Geology and mineral deposits of the Colfax and Foresthill Quadrangles, California. California Division of Mines Special Report 67, 50 p.
FERGUSON, H. G., and GANNETT, R. W. (1932) Gold quartz veins of the Allegheny district, California. U.S. Geological Survey Professional Paper 172, 139 p.
JOHNSTON, W. D., JR. (1944) The gold quartz veins of Grass Valley, California. U.S. Geological Survey Professional Paper 194, 101 p.
KNOPF, A. (1929) The Mother Lode system of California. U.S. Geological Survey Professional Paper 157, 88 p.
LEICHT, D. (1982) What's New in Minerals? Mineralogical Record, 13, 385.
LINDGREN, W. (1895) Characteristic features of California gold quartz veins. Geological Society of America Bulletin, 6, p. 221-240.
LOGAN, C. A. (1935) Mother Lode gold belt of California. California Division of Mines Bulletin 108, 240 p.
RANSOME, F. L. (1900) Mother Lode District. U.S. Geological Survey Folio 63, 11 p.
Wayne C. Leicht
875 North Coast Highway
Laguna Beach, California 92651-1415
(949) 494-5155; e-mail: email@example.com
Department of Geology and Geography
Auburn, Alabama 36849-5305
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|Author:||Leicht, Wayne C.; Cook, Robert|
|Publication:||The Mineralogical Record|
|Date:||Jan 1, 2004|
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