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Placerville Mining District, Mother Lode Belt, El Dorado Co., California, USAi
Regional Level Types
Placerville Mining DistrictMining District
Mother Lode BeltBelt
El Dorado Co.County
CaliforniaState
USACountry

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Key
Latitude & Longitude (WGS84):
38° 43' 19'' North , 120° 48' 25'' West
Latitude & Longitude (decimal):
Locality type:


Location: Placerville is a Au-Pt mining area in west-central El Dorado County in secs. 12, 13, 24, 29, T10N, R 10E; secs. 3-10, 15-22, 29 & 30, T10N, R11E; secs. 35 & 36, T11N, R10E; secs. 28, 29, & 31-33, T11N, R11E, MDM. Discovered in 1848. The district includes the lode mines of the Mother Lode belt, which extends north through the district, and the placer deposits here and in the adjacent Smith Flat, Diamond Springs, Texas Hill, Coon Hollow, and White Rock areas.

The Placerville District is one of the most important Tertiary placer-gold mining districts in the northern Sierra Nevada. The district is noted for several large hydraulic and drift mines within auriferous Eocene channel gravels deposited by numerous southwestward flowing tributaries of the ancestral South Fork of the American River.

Ores consisted of channel lag and bench gravels deposited on the eroded bedrock surface and adjacent floodplains, and later elevated and exposed by uplift and downcutting of modern drainages. They were preserved under a sequence of volcanic deposits of the Tertiary Valley Springs and Mehrten formations, which blanket most of the gravels in the Placerville District. The gravels were laden with placer gold from the erosion of the bedrock gold-quartz veins through which the rivers flowed. Secondary deposits were encountered overlying the basal gravels in a section of younger interbedded channel gravels and volcanic flows. These "intervolcanic" gravels, while often barren, were sometimes charged with placer gold by erosion of the older auriferous channel gravels.

The principle gravel deposit, the "Deep Blue Lead", is expressed as a bedrock erosional channel which transects the east half of the district from northeast to southwest. Other important gravel deposits include those of the Coon Hollow and Spanish Hill-Green Mountain channels on the west end of the district. These gravels are considerably richer than those of the Deep Blue Lead, having eroded the gold-bearing Mother Lode quartz veins in the central and western parts of the district.

The gold particles are in some places associated with platinum and almost invariably associated with black sands composed of magnetite, ilmenite, chromite, and pyrite derived from basic bedrock such as diabase, gabbro, and serpentine.

Commodities: Placer deposits: Placer gold dust to large nuggets; Lode deposits: free-milling, gold-bearing quartz veins and sulfides; ore materials: native gold and sulfides (lode); gangue materials: quartz, volcanic, granitic, and metamorphic gravels.

History: Gold was discovered in the Placerville area in July 1848. The town was first known as Dry Diggings but had the nickname of Old Hangtown; three robbers were hanged here on October 17, 1849. From the middle 1850's through the 1870's, the hydraulic and drift mines in the district were extremely rich. One 20-acre claim at Coon Hollow yielded $5 million, and the Spanish Hill area yielded $6 million. Quartz mining began in 1852 at the Pacific mine, but the chief period of lode mining was from the 1880's until about 1915. There was some mining in the district again in the 1930's, but there has been little activity since. Many of the mines in the district came under the control of the Placerville Gold Mining Company.

Placer gold was discovered in Hangtown Creek in the Placerville area in July 1848. Initially, placer production from Hangtown Creek reached approximately 1,000 ounces of gold per week. As word spread, a rush to the area ensued and the town of Dry Diggings was established (nicknamed ?Old Hangtown? in reference to the hanging of three robbers here in October, 1849). The town was later renamed Placerville.

By fall of 1849 the miners working Hangtown Creek had discovered Tertiary river gravel laying exposed on both sides of Spanish Hill. The Spanish Hill miners began "coyoting" under the hill where they found the auriferous gravel in channels generally running west by southwest. Names such as "Coon Hollow Channel" and the "Deep Blue Lead" were adopted by the miners to identify these gold producing channels. One 49 er, J.M. Letts described the process of coyoting at Spanish Hill? "It was by digging holes or pits in the ground - generally into the base of the mountains - sometimes penetrating to a depth of 50 - 100 feet with an opening just sufficient to admit a man." (Noble, 2002).

Mining at Spanish Hill paid extremely well but remained primitive until 1854 when the South Fork & Placerville Canal Company completed 16 miles of flume, which brought much needed water to Spanish Hill and Coon Hollow for hydraulic mining. By December of that year, the entire top of Spanish Hill had been washed out to a depth of 60 feet (Noble, 2002).

At Coon Hollow, the gravel was removed by drifting from 1852 to 1861, and between 1861 and 1871 by hydraulic mining.

From the middle 1850's through the 1870's, numerous hydraulic and drift mines were discovered and worked intermittently until as late as the 1930's. Quartz mining began in 1852 at the Pacific Mine, but the chief period of lode mining was from the 1880 to about 1915.

Many of the mines (Lode and drift, and hydraulic) in the district came under the control of the Placerville Gold Mining Company, which was incorporated in 1911, and was a successor to the Placerville Gold Quartz Company, LTD., an English concern that was originally incorporated in 1878. (Clark and Carlson, 1956). The Placerville Gold Mining Company controlled 1,400 acres in all. Many of these claims were early day producers of which only fragmentary histories remain (Logan, 1934).

Geology: A belt of gray to black slate of the Mariposa Formation (Upper Jurassic) one to two miles wide extends north through the central portion of the district. Greenstone and amphibolite are to the west, and schist and slate of the Calaveras Formation (Carboniferous to Permian) and granodiorite lie to the east. The Tertiary South Fork of the American River, which has numerous tributaries, entered the Placerville basin from Newtown. In places the Tertiary gravels are overlain by thick beds of rhyolite tuff and andesite.

While the Placerville District includes some Mother Lode quartz lode mines, it is best known for its highly productive Tertiary channel deposits, the most important being at Coon Hollow, Diamond Springs, Smith's Flat, Texas Hill, and White Rock.

The Placerville District straddles the Melones Fault zone and hence bedrock varies from east to west across the district. A belt of Mother Lode Mariposa Formation gray to black approximately one to two miles wide extends northward through the district. To the east, bedrock is schist and slate of the Calaveras Complex and granodiorite. To the west, bedrock is amphibolite and greenstone (Clark, 1970).

The district is situated on a ridge between the South Fork of the American River (American River) and Weber Creek, on which occur remnants of channel gravels deposited by southward flowing tributaries to the ancestral South Fork of the American River. Gravels deposited within the main channel of the American River, which approximately followed the course of Weber Creek, have been largely lost to erosion.

The gravel deposits are largely overlain by overlain by thick beds of rhyolite tuff and andesite. In the Placerville area, the Valley Springs Formation coinsist of generally flat lying beds of rhyolite tuff. The tuff usually is fine grained and contains small crystals of black biotite. Smaller amounts of breccia, conglomerate, and siltstone are present (Clark and Carlson, 1956). The overlying Mehrten Formation occupies many of the interstream ridges and consists chiefly of andesitic volcanic debris composed of boulders, cobbles, and pebbles.

Placerville District gravels are generally composed of pebbles and boulders of quartz, chert, granitic and volcanic rocks interbedded with clay and sand. Considerable amounts of placer gold is present at or near the bottom of these deposits (Clark and Carlson, 1956). Generally, the gold on bedrock was smooth and coarse. Associated with the gold in the placer deposits are magnetite and other heavy resistant minerals such as ilmenite, garnet, rutile, zircon, and platinum-group metals.

The richest gravels in the Placerville District were those at Coon Hollow, just southwest of Placerville, and just west and downstream of the Mother Lode bedrock quartz veins (Lindgren, 1911). Lindgren (1911) describes a number of the individual deposits in greater detail.

The ancestral Tertiary American River and its tributaries entered the district from the northeast. The most productive tributaries from east to west across the district were the Deep Blue Lead, Spanish Hill-Green Mountain Channel, and the Coon Hollow Channel.

Deep Blue Lead Channel: Of the numerous American River tributaries in this district, the best known was the Deep Blue Lead. It entered the northeast corner of the district and extended southward for about 2 miles from White Rock Canyon to Smith's Flat and then west-southwest through Texas Hill to Cedar Ravine.

The Blue Lead channel consists of a deep, fairly straight channel flanked by broad sweeping and curving benches. This tributary followed a bedrock slate-granodiorite contact for several miles and is believed to have derived much of its gold from many small veins in the contact zone. The general course of the Deep Blue Lead was from north-northeast to south-southwest. At White Rock, the exposed gravels were hydraulically mined, producing about $5 million. The bedrock channel at White Rock was 30 feet wide with 12 feet of gravel. Two benches 40 feet high also yielded paying gravel (Lindgren, 1911). For about 2 miles from White Rock to Smith Flat, where the gravels were overlain by the Valley Springs and Mehrten formation rocks, the channel was almost continuously drift mined. From Smith Flat, the Deep Blue Lead trended west-southwest for another 2 miles to Texas Hill where it was again mined hydraulically. For most of this stretch, the channel was developed by the Bendfelt, Hook & Ladder, Lyon, Kumfa, Try Again, Texas Hill, Clark, Rivera, and Linden drift mines (Lindgren, 1911). The Lyon Mine produced $1.4 million. At the Benfield Mine, a gravel deposit some five feet thick and 50 to 120 feet wide yielded $2 to $8 per ton. Blue Lead gravels were generally not as rich as those to the west in channels crossing the Mother Lode quartz belt. Blue Lead gravels were deposited before the beginning of the later rhyolitic flows, for cobbles of rhyolite are contained in all of them (Lindgren, 1911).
Coon Hollow Channel

The Coon Hollow channel was the richest of the Placerville district's placer deposits, having produced about $10 million. This channel is in the western part of the district and its deposits are thought to have been enriched by erosion of bedrock Mother Lode gold veins. The Coon Hollow deposits contained 3 gravel pay streaks, the first on bedrock, the second 25 feet above, and the third 60 feet above. The first and third were very rich (Lindgren, 1911). Coon Hollow gravels were much richer than the gravels of the Blue Lead or Spanish Hill - Green Mountain channels. Overall, the entire section of gravel was at least 100 feet thick and averaged about $1 per yard (Lindgren, 1911). A single claim of 20 acres (Excelsior claim) produced $5 million from gravels containing as much as $5 per cubic yard.

Total width of the Coon Hollow bedrock channel was 2,000 feet. The third streak was reportedly 300 feet wide. Part of the gravel was cemented. Unlike the gravels farther east, there were no volcanic pebbles in the Coon Hollow gravels (Lindgren, 1911).

Spanish Hill-Green Mountain Channel: The Spanish Hill-Green Mountain Channel, in the south central part of the district, formed a well-defined tributary to the main river channel and was separated from the Deep Blue Lead to the east and the Coon Hollow channel to the west by pronounced intervening bedrock ridges (Lindgren, 1911). Several mines exploited these channel deposits including the important Spanish Hill hydraulic mine, which produced $6 million, Cedar Springs, and Green Mountain drift mines. In the Cedar Springs Mine, the bedrock channel was 300 to 600 feet wide with pay gravel 4 to feet thick.

Ore Deposits: Of the numerous tributaries of the main Tertiary channel in this district, probably the best known and one of the richest was the Deep Blue Lead. This channel extended south from White Rock to Smith's Flat and then west-southwest through the Texas Hill area. The lode-gold deposits arc massive quartz veins as much as 20 feet thick with numerous parallel stringers. The ore bodies are low to moderate in grade (y, to y. ounce of gold per ton), but the veins have been mined to depths of 2,000 feet. The ore contains finely disseminated free gold and small amounts of pyrite. The veins occur chiefly in slate.

Workings: The Placerville District gravel deposits were generally worked by small- to medium-sized drift mines with access through shallow shafts or through adits generally less than 2,000 feet long, and/or large scale hydraulic mining operations. Consequently, there is meager information regarding specific mine workings. Limited information about some of the districts drift mines is contained in unpublished historical files of the California Geological Survey and other published sources (Noble, 2002). Specifics of the hydraulically mined deposits are even more scarce. Generic discussions of these mining techniques follow:

Drift Mining: Drift mining involved driving adits and tunnels along or close to the lowest point in the bedrock trough of an ancient channel and following it upstream along the bedrock surface. Some deeply buried drift mines were originally accessed through vertical shafts requiring timbering, headframes, hoisting, and pumping equipment. Larger shafts were seldom over 3 compartments Smaller mines often had single compartment shafts as small as 2 x 5 feet. Since considerable water was associated with the gravels, it was a serious problem in deeper shafts and costly pumping was required. By the 1890's, due to drainage problems and the expense of hoisting, most major drift mines were accessed through tramway and drain tunnels driven into bedrock below the channels.

Channels were usually located by gravel exposures on hillsides and terraces. Exposures of upstream and downstream gravels were called "inlets" and "outlets," respectively. Where a ravine or canyon cut into, but not through an old channel, the exposure was called a "breakout."

The preferred method of developing an inlet was to tunnel through bedrock under the channel at such a depth and angle as to break through into the bed of the channel providing natural drainage. The overlying gravels could then be accessed directly through the tunnel or by periodic raises and drifts. Development of an outlet involved following the bedrock channel directly into the hillside, the incline of the bedrock providing natural drainage. The tunnel entrances were usually in or near a ravine or gulch to aid in waste-rock disposal.

Prospecting and developing a breakout was more difficult, since the exposed gravel could be in the basal channel or hundreds of feet up on the edge of the channel, making it impossible to locate a prospect tunnel with any certainty. The surest method of prospecting was to run an incline on the pitch of the bedrock. Another method was to sink a vertical shaft on the presumed channel axis. The former method proved superior since it involved less subjectivity and often uncovered paying bench gravels on edges of the old stream. Once the bed of the channel was located, it was prospected by drifts and cross cuts to ascertain width, direction, grade, and the location, extent, and quality of pay.

Access tunnels were driven in bedrock to minimize timbering and ensure a stable roof, through which upraises were driven to work the placer gravels. Tunnels were generally run under the lowest point of the bed of the channel in order to assure natural drainage and to make it possible to take auriferous gravels out of the mine without having to hoist it.

The main drifts were kept as straight as possible and in the center or lowest depression of the channel. To prospect the width of the channel, crosscuts at right angles to the drift were driven on each side to the rims of the channels or the limit of the paying lead. These were timbered and lagged in soft gravels, but not to the extent of the main drift. In wide pay leads, gangways paralleled the main tunnel to help block out the ore in rectangular blocks. In looser gravels, timbering was required and the main difficulty was preventing caving until timbering was in place. The looser gravels were excavated with pick and shovel. Up until the late 1800's, most workings were driven by hand, then later by machine and pneumatic drills.

Working drifts in the gravel beds and pay leads themselves were larger than the bedrock tunnels and usually timbered due to their extended and long-term use. In wide gravel deposits, as a precaution against caving, gravel pillars from 20 - 40 feet wide were left on each side of the drift. When the main access tunnel was in bedrock following the line of the channel, pillars were not required, as the tunnel in the gravel was only for temporary use in mining the ground between its connections with the bedrock tunnel. Raises to access the gravel were made every 200 - 400 feet as necessary.

The breaking out of gravel (breasting) was done from the working faces of drifts. Usually, 1-2 feet of soft bedrock and 3-4 feet of gravel were mined out to advance the face. When the gravels were well-cemented, blasting was required. Otherwise the material could be removed with picks. Boulder sized material was left underground and only the gravels and fines were removed from the mine.

Bedrock swelling was a frequent problem. Tunnels on and within bedrock were sometimes affected by the upward swelling of the bedrock. In these cases, heavy timbering was required and the tunnel floor had to be periodically cut and lowered to keep the tunnel open.

Soft or fractured slates were the most favorable bedrock. The surface was usually creviced and weathered enough that gold could be found to a depth of 1 foot in the top of the bedrock. Where sufficiently weathered and soft, this upper bedrock layer could be easily removed. If the surface of the bedrock was too hard to be worked, it was cleaned thoroughly, and the crevices and surface were worked with special tools to remove every particle of gold.

According to the gravel's hardness, they were either washed through sluices or crushed in stamp mills. Much of the gravel was so highly cemented it had to be milled several times. Stamp mills with coarse screens were also found to be suitable for milling cemented gravel. For soft and uncemented gravels, a dump, sluices, and water supply under generally low pressure comprised the entire surface workings.

Ventilation of mines was accomplished by direct surface connection through the use of boreholes and the mine shafts and tunnels. It relied on natural drafts, drafts by fire, falling water, or blowers. Within the mines, arrangements of doors were often used to direct the flow of air through the tunnels, drifts, and breasts.

Ore was removed by ore cars of various capacity determined by available power and tunnel size. In smaller mines, small cars were often pushed by hand. In larger mines using horsepower or trains, larger two ton cars could be brought out in trains of 5-10 cars.
Hydraulic Mining

Hydraulic mining methods were first applied in the Placerville District in 1854 at Spanish Hill. Hydraulic mining allowed the bulk processing of large volumes of low yield that would otherwise be unprofitable by other methods of mining. Hydraulic mining involved directing a powerful stream of high pressure water through large nozzles called monitors or "giants" at the base of a gravel bank, undercutting it and allowing it to collapse. Large gravel banks several hundred feet high were mined in this manner, but larger banks were often hydraulicked in two or more benches. In some cases, adits were driven into the exposed face and loaded with explosives to help break down the exposure. The resulting slurry of clay, sand, gravel, and gold was washed through sluice boxes to trap the gold. The sluice boxes were generally four feet wide and deep and often over a thousand feet long and lined with riffles or over devices to mechanically trap the gold. Mercury was added to amalgamate the finer gold. The remaining debris was indiscriminately dumped in the nearest available stream or river.

One of hydraulic mining's highest costs was in the ditches, flumes, and reservoirs needed to supply sufficient volumes of water at high pressure. A mine usually needed its own system of ditches and flumes to deliver water from distant and higher reservoirs or rivers. A mine might have 10-20 or more miles of ditches as well as dams and reservoirs, flumes, and tunnels. At the mine site, the water fell through large iron pipes into the monitors. Hydraulic mining flourished for about 30 years until the mid-1880's when the Sawyer Decision curtailed debris disposal.

Another expensive undertaking was often finding an outlet for the debris. As the gravels were washed lower and lower in the ancient channel beds, it was often necessary to drive a tunnel through the bedrock channel rim to drain the workings into a nearby valley.

Production: The value of the total output of the Placerville District is unknown, but the placer mines are estimated to have yielded at least $25 million, and lode mines at least $2 million.

Mines: Lode: Elliott, Epley ($100,000+), Griffith, Guildford ($200,000+), Harmon ($100,000+), Larkin ($125,000), Margurite, Oregon ($100,000+), Pacific ($1,486,000), River Hill, Sherman ($136,000), Superior, True Consolidated ($100,000), Van Hooker ($100,000+).Placer: Coon Hollow ($10 million), Diamond Springs, Green Mountain, Negro Hill, Sacramento Hill, Spanish Hill ($6 million), Smith's Flat ($2 million+), Texas Hill, White Rock ($5 million). Drift: Benfield, Cedar Spring, Clark, Kumfa, Landecker, Lyon, Pascoe, Rivera, Texas Hill, Try Again, Union.

Regions containing this locality

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Standard Detailed Strunz Dana Chemical Elements

Commodity List

This is a list of exploitable or exploited mineral commodities recorded from this region.


Mineral List

Mineral list contains entries from the region specified including sub-localities

17 valid minerals.

Rock Types Recorded

Note: this is a very new system on mindat.org and data is currently VERY limited. Please bear with us while we work towards adding this information!

Rock list contains entries from the region specified including sub-localities

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Alphabetical List Tree Diagram

Detailed Mineral List:

Anatase
Formula: TiO2
Description: Occurs as minute crystals with brookite on quartz crystals.
Reference: Kunz, George Frederick (1892), Mineralogical notes on brookite, octahedrite, quartz, and ruby: American Journal of Science, 3rd. series: 43: 329-330; Kunz, George Frederick (1892), Octahedrite (anatase) near Placerville, El Dorado County: Mineralogical Magazine: 9: 395; Kunz, George Frederick (1893), Mineralogical notes on brookite, octahedrite, and quartz: California Mining Bureau. Report 11: 207-209; Kunz, George Frederick (1901), Octahedrite (anatase) from Placerville, El Dorado County: Mineralogical Magazine: 9: 394; Murdoch, Joseph & Robert W. Webb (1966), Minerals of California, Centennial Volume (1866-1966): California Division Mines & Geology Bulletin 189: 72, 114.
Ankerite
Formula: Ca(Fe2+,Mg)(CO3)2
Description: Occurs as a gangue mineral in gold-quartz veins.
Reference: Logan, Clarence August (1934), Mother Lode gold belt of California: California Division Mines Bulletin 108, 221 pp.: 30; Murdoch, Joseph & Robert W. Webb (1966), Minerals of California, Centennial Volume (1866-1966): California Division Mines & Geology Bulletin 189: 76.
Arsenopyrite
Formula: FeAsS
Reference: USGS (2005), Mineral Resources Data System (MRDS): U.S. Geological Survey, Reston, Virginia, loc. file ID #10310663.
Brookite
Formula: TiO2
Reference: Kunz, George Frederick (1892), Mineralogical notes on brookite, octahedrite, quartz, and ruby: American Journal of Science, 3rd. series: 43: 329-330; Kunz, George Frederick (1892), Octahedrite (anatase) near Placerville, El Dorado County: Mineralogical Magazine: 9: 395; Kunz, George Frederick (1893), Mineralogical notes on brookite, octahedrite, and quartz: California Mining Bureau. Report 11: 207-209; Kunz, George Frederick (1901), Octahedrite (anatase) from Placerville, El Dorado County: Mineralogical Magazine: 9: 394; Kunz, George Frederick (1905a), Gems, jewelers’ materials, and ornamental stones of California: California Division Mines Bulletin 37, 171 pp.: 106; Murdoch, Joseph & Robert W. Webb (1966), Minerals of California, Centennial Volume (1866-1966): California Division Mines & Geology Bulletin 189: 72, 114.
Carnotite
Formula: K2(UO2)2(VO4)2 · 3H2O
Description: Represented by California Division of Mines and Geology specimen #21635.
Reference: Murdoch, Joseph & Robert W. Webb (1966), Minerals of California, Centennial Volume (1866-1966): California Division Mines & Geology Bulletin 189: 120.
Clinochlore
Formula: Mg5Al(AlSi3O10)(OH)8
Reference: Knopf, Adolf (1929), The Mother Lode system of California: USGS PP 157, 88 pp: 37; Pemberton, H. Earl (1983), Minerals of California; Van Nostrand Reinholt Press: 434.
Clinochlore var: Ripidolite
Formula: (Mg,Fe,Al)6(Si,Al)4O10(OH)8
Reference: Knopf, Adolf (1929), The Mother Lode system of California: USGS PP 157, 88 pp: 37; Pemberton, H. Earl (1983), Minerals of California; Van Nostrand Reinholt Press: 434.
Diamond
Formula: C
Galena
Formula: PbS
Gold
Formula: Au
Localities: Reported from at least 113 localities in this region.
Graphite
Formula: C
Description: Occurs as graphitic slate.
Reference: USGS (2005), Mineral Resources Data System (MRDS): U.S. Geological Survey, Reston, Virginia, loc. file ID #10101129.
Maldonite
Formula: Au2Bi
Description: Founf in 1899 and represented by CDMG specimen #15391. 60% Au & 40% Bi.
Reference: Murdoch, Joseph & Robert W. Webb (1966), Minerals of California, Centennial Volume (1866-1966): California Division Mines & Geology Bulletin 189: 106; Pemberton, H. Earl (1983), Minerals of California; Van Nostrand Reinholt Press: 18 (map 2-7), 37; Bernard, Jan H.and Jaroslav Hyrsl (2004), Minerals and their Localities: 374.
'Manganese Oxides'
Reference: USGS (2005), Mineral Resources Data System (MRDS): U.S. Geological Survey, Reston, Virginia, loc. file ID #10030182.
'Mariposite'
Formula: K(Al,Cr)2(Al,Si)4O10(OH)2
Molybdenite
Formula: MoS2
Reference: Trask, John Boardman (1856), Report on the geology of northern and southern California: California Legislature, 7th. sess., Ap. to Jour. S. Doc. 14, 66 pp.: 28; Murdoch, Joseph & Robert W. Webb (1966), Minerals of California, Centennial Volume (1866-1966): California Division Mines & Geology Bulletin 189: 268.
Muscovite
Formula: KAl2(AlSi3O10)(OH)2
Muscovite var: Phengite
Formula: KAl1.5(Mg,Fe)0.5(Al0.5Si3.5O10)(OH)2
Pyrite
Formula: FeS2
Pyrite var: Auriferous Pyrite
Formula: FeS2
Reference: USGS (2005), Mineral Resources Data System (MRDS): U.S. Geological Survey, Reston, Virginia, loc. file ID #10310663.
Quartz
Formula: SiO2
Localities: Reported from at least 68 localities in this region.
Quartz var: Rock Crystal
Formula: SiO2
Description: Includes phantoms; best in the state.
Reference: Hanks, Henry Garber (1884), Fourth report of the State Mineralogist: California Mining Bureau. Report 4, 410 pp.: 65; Kunz, George Frederick (1892), Mineralogical notes on brookite, octahedrite, quartz, and ruby: American Journal of Science, 3rd. series: 43: 329-330; Kunz, George Frederick (1892), Octahedrite (anatase) near Placerville, El Dorado County: Mineralogical Magazine: 9: 395; Kunz, George Frederick (1893), Precious stones: Mineral Resources U.S., 1891: 547; Murdoch, Joseph & Robert W. Webb (1966), Minerals of California, Centennial Volume (1866-1966): California Division Mines & Geology Bulletin 189: 313.
Quartz var: Smoky Quartz
Formula: SiO2
Reference: Hanks, Henry Garber (1884), Fourth report of the State Mineralogist: California Mining Bureau. Report 4, 410 pp.: 65; Kunz, George Frederick (1892), Mineralogical notes on brookite, octahedrite, quartz, and ruby: American Journal of Science, 3rd. series: 43: 329-330; Kunz, George Frederick (1892), Octahedrite (anatase) near Placerville, El Dorado County: Mineralogical Magazine: 9: 395; Kunz, George Frederick (1893), Precious stones: Mineral Resources U.S., 1891: 547; Murdoch, Joseph & Robert W. Webb (1966), Minerals of California, Centennial Volume (1866-1966): California Division Mines & Geology Bulletin 189: 313.
Silver
Formula: Ag
Reference: U.S. Geological Survey, 2005, Mineral Resources Data System: U.S. Geological Survey, Reston, Virginia.
Talc
Formula: Mg3Si4O10(OH)2

List of minerals arranged by Strunz 10th Edition classification

Group 1 - Elements
Diamond1.CB.10aC
Gold1.AA.05Au
Graphite1.CB.05aC
Silver1.AA.05Ag
Group 2 - Sulphides and Sulfosalts
Arsenopyrite2.EB.20FeAsS
Galena2.CD.10PbS
Maldonite2.AA.40Au2Bi
Molybdenite2.EA.30MoS2
Pyrite2.EB.05aFeS2
var: Auriferous Pyrite2.EB.05aFeS2
Group 4 - Oxides and Hydroxides
Anatase4.DD.05TiO2
Brookite4.DD.10TiO2
Carnotite4.HB.05K2(UO2)2(VO4)2 · 3H2O
Quartz4.DA.05SiO2
var: Rock Crystal4.DA.05SiO2
var: Smoky Quartz4.DA.05SiO2
Group 5 - Nitrates and Carbonates
Ankerite5.AB.10Ca(Fe2+,Mg)(CO3)2
Group 9 - Silicates
Clinochlore9.EC.55Mg5Al(AlSi3O10)(OH)8
var: Ripidolite9.EC.55(Mg,Fe,Al)6(Si,Al)4O10(OH)8
Muscovite9.EC.15KAl2(AlSi3O10)(OH)2
var: Phengite9.EC.15KAl1.5(Mg,Fe)0.5(Al0.5Si3.5O10)(OH)2
Talc9.EC.05Mg3Si4O10(OH)2
Unclassified Minerals, Rocks, etc.
'Manganese Oxides'-
'Mariposite'-K(Al,Cr)2(Al,Si)4O10(OH)2

List of minerals arranged by Dana 8th Edition classification

Group 1 - NATIVE ELEMENTS AND ALLOYS
Metals, other than the Platinum Group
Gold1.1.1.1Au
Maldonite1.1.3.1Au2Bi
Silver1.1.1.2Ag
Semi-metals and non-metals
Diamond1.3.6.1C
Graphite1.3.6.2C
Group 2 - SULFIDES
AmXp, with m:p = 1:1
Galena2.8.1.1PbS
AmBnXp, with (m+n):p = 1:2
Arsenopyrite2.12.4.1FeAsS
Molybdenite2.12.10.1MoS2
Pyrite2.12.1.1FeS2
Group 4 - SIMPLE OXIDES
AX2
Anatase4.4.4.1TiO2
Brookite4.4.5.1TiO2
Group 14 - ANHYDROUS NORMAL CARBONATES
AB(XO3)2
Ankerite14.2.1.2Ca(Fe2+,Mg)(CO3)2
Group 40 - HYDRATED NORMAL PHOSPHATES,ARSENATES AND VANADATES
AB2(XO4)2·xH2O, containing (UO2)2+
Carnotite40.2a.28.1K2(UO2)2(VO4)2 · 3H2O
Group 71 - PHYLLOSILICATES Sheets of Six-Membered Rings
Sheets of 6-membered rings with 2:1 layers
Muscovite71.2.2a.1KAl2(AlSi3O10)(OH)2
Talc71.2.1.3Mg3Si4O10(OH)2
Sheets of 6-membered rings interlayered 1:1, 2:1, and octahedra
Clinochlore71.4.1.4Mg5Al(AlSi3O10)(OH)8
Group 75 - TECTOSILICATES Si Tetrahedral Frameworks
Si Tetrahedral Frameworks - SiO2 with [4] coordinated Si
Quartz75.1.3.1SiO2
Unclassified Minerals, Mixtures, etc.
Clinochlore
var: Ripidolite
-(Mg,Fe,Al)6(Si,Al)4O10(OH)8
'Manganese Oxides'-
'Mariposite'-K(Al,Cr)2(Al,Si)4O10(OH)2
Muscovite
var: Phengite
-KAl1.5(Mg,Fe)0.5(Al0.5Si3.5O10)(OH)2
Pyrite
var: Auriferous Pyrite
-FeS2
Quartz
var: Rock Crystal
-SiO2
var: Smoky Quartz-SiO2

List of minerals for each chemical element

HHydrogen
H Clinochlore (var: Ripidolite)(Mg,Fe,Al)6(Si,Al)4O10(OH)8
H CarnotiteK2(UO2)2(VO4)2 · 3H2O
H TalcMg3Si4O10(OH)2
H MaripositeK(Al,Cr)2(Al,Si)4O10(OH)2
H ClinochloreMg5Al(AlSi3O10)(OH)8
H MuscoviteKAl2(AlSi3O10)(OH)2
H Muscovite (var: Phengite)KAl1.5(Mg,Fe)0.5(Al0.5Si3.5O10)(OH)2
CCarbon
C AnkeriteCa(Fe2+,Mg)(CO3)2
C DiamondC
C GraphiteC
OOxygen
O QuartzSiO2
O AnkeriteCa(Fe2+,Mg)(CO3)2
O Clinochlore (var: Ripidolite)(Mg,Fe,Al)6(Si,Al)4O10(OH)8
O AnataseTiO2
O BrookiteTiO2
O CarnotiteK2(UO2)2(VO4)2 · 3H2O
O Quartz (var: Rock Crystal)SiO2
O Quartz (var: Smoky Quartz)SiO2
O TalcMg3Si4O10(OH)2
O MaripositeK(Al,Cr)2(Al,Si)4O10(OH)2
O ClinochloreMg5Al(AlSi3O10)(OH)8
O MuscoviteKAl2(AlSi3O10)(OH)2
O Muscovite (var: Phengite)KAl1.5(Mg,Fe)0.5(Al0.5Si3.5O10)(OH)2
MgMagnesium
Mg AnkeriteCa(Fe2+,Mg)(CO3)2
Mg Clinochlore (var: Ripidolite)(Mg,Fe,Al)6(Si,Al)4O10(OH)8
Mg TalcMg3Si4O10(OH)2
Mg ClinochloreMg5Al(AlSi3O10)(OH)8
Mg Muscovite (var: Phengite)KAl1.5(Mg,Fe)0.5(Al0.5Si3.5O10)(OH)2
AlAluminium
Al Clinochlore (var: Ripidolite)(Mg,Fe,Al)6(Si,Al)4O10(OH)8
Al MaripositeK(Al,Cr)2(Al,Si)4O10(OH)2
Al ClinochloreMg5Al(AlSi3O10)(OH)8
Al MuscoviteKAl2(AlSi3O10)(OH)2
Al Muscovite (var: Phengite)KAl1.5(Mg,Fe)0.5(Al0.5Si3.5O10)(OH)2
SiSilicon
Si QuartzSiO2
Si Clinochlore (var: Ripidolite)(Mg,Fe,Al)6(Si,Al)4O10(OH)8
Si Quartz (var: Rock Crystal)SiO2
Si Quartz (var: Smoky Quartz)SiO2
Si TalcMg3Si4O10(OH)2
Si MaripositeK(Al,Cr)2(Al,Si)4O10(OH)2
Si ClinochloreMg5Al(AlSi3O10)(OH)8
Si MuscoviteKAl2(AlSi3O10)(OH)2
Si Muscovite (var: Phengite)KAl1.5(Mg,Fe)0.5(Al0.5Si3.5O10)(OH)2
SSulfur
S PyriteFeS2
S GalenaPbS
S MolybdeniteMoS2
S Pyrite (var: Auriferous Pyrite)FeS2
S ArsenopyriteFeAsS
KPotassium
K CarnotiteK2(UO2)2(VO4)2 · 3H2O
K MaripositeK(Al,Cr)2(Al,Si)4O10(OH)2
K MuscoviteKAl2(AlSi3O10)(OH)2
K Muscovite (var: Phengite)KAl1.5(Mg,Fe)0.5(Al0.5Si3.5O10)(OH)2
CaCalcium
Ca AnkeriteCa(Fe2+,Mg)(CO3)2
TiTitanium
Ti AnataseTiO2
Ti BrookiteTiO2
VVanadium
V CarnotiteK2(UO2)2(VO4)2 · 3H2O
CrChromium
Cr MaripositeK(Al,Cr)2(Al,Si)4O10(OH)2
FeIron
Fe PyriteFeS2
Fe AnkeriteCa(Fe2+,Mg)(CO3)2
Fe Clinochlore (var: Ripidolite)(Mg,Fe,Al)6(Si,Al)4O10(OH)8
Fe Pyrite (var: Auriferous Pyrite)FeS2
Fe ArsenopyriteFeAsS
Fe Muscovite (var: Phengite)KAl1.5(Mg,Fe)0.5(Al0.5Si3.5O10)(OH)2
AsArsenic
As ArsenopyriteFeAsS
MoMolybdenum
Mo MolybdeniteMoS2
AgSilver
Ag SilverAg
AuGold
Au GoldAu
Au MaldoniteAu2Bi
PbLead
Pb GalenaPbS
BiBismuth
Bi MaldoniteAu2Bi
UUranium
U CarnotiteK2(UO2)2(VO4)2 · 3H2O

References

Sort by

Year (asc) Year (desc) Author (A-Z) Author (Z-A)
Irelan, William, Jr. (1888b), Eighth annual report of the State Mineralogist [includes mineral resources of the State, with contributions by W.A. Goodyear, H.A. Whiting, and Stephen Bowers]: California Mining Bureau. (Report 8), 946 pp.: 181-187.
De Groot, Henry (1890), Alpine, El Dorado, Inyo, Mono, San Bernardino Counties: California Mining Bureau (Report 10): 10: 179-180.
Lindgren, Waldemar & Henry Ward Turner (1894), Description of the gold belt, California; description of the Placerville sheet: USGS Geol. Atlas, Placerville folio (Folio No. 3) 3 pp.; […(abstract): Jour. Geol.: 4: 248-250 (1896)].
Rowlands, R. (1894), Map of the principal gravel mines in the vicinity of Placerville: California Mining Bureau (Report 12): 100.
Rowlands, R. (1894), Map of the principal gravel mines in the vicinity of Placerville: California State Mining Bureau, 12th Annual Report of the Sate Mineralogist (Report 12): 100, 293-295.
Lindgren, Waldemar (1911), The Tertiary gravels of the Sierra Nevada of California: USGS Professional Paper 73, 226 pp.: 171-180.
Tucker, W. Burling, and Waring, C.A. (1916), Mines and mineral resources of El Dorado, Placer, Sacramento, and Yuba counties: California State Mining Bureau, 15th Report of the State Mineralogist (Report 15): 283-299.
Tucker, W. Burling & C.A. Waring (1919), El Dorado County: California Journal of Mines and Geology, California Mining Bureau. (Report 15): 15: 293-295.
Logan, Clarence August (1934), Mother Lode Gold Belt of California: California Division Mines Bulletin 108, 221 pp.: 26-27, 35, 52.
Logan, Clarence August (1938), Mineral resources of El Dorado County: California Journal of Mines and Geology, California Division Mines (Report 34): 34(3): 251-253.
Clark, Wm. B. & D.W. Carlson (1956), Mines and mineral resources of El Dorado County, California: California Journal of Mines and Geology: 52(4): 422-423, 432-434.
Clark, L.D. (1964), Stratigraphy and Structure of Part of the Western Metamorphic Belt, California, USGS Professional Paper 410, 70 pp.
Clark, Wm. B. (1970a) Gold districts of California: California Division Mines & Geology Bulletin 193: 107.
Duffield, W.A. and Sharp, R.V. (1975), Geology of the Sierra foothills melange and adjacent areas, Amador County, California: USGS Professional Paper 827, 30 p.
Saleeby, Jason (1982), Polygenetic ophiolite belt of the California Sierra Nevada: Geochronological and tectonostratigraphic development: Journal of Geophysical Research: 87(8): 1803-1824.
Earhart, R. L. (1988), Geologic setting of gold occurrences in the Big Canyon area, El Dorado County, California: USGS Professional Paper 1576, 13 p.
Busch, L.L. (2001), Mineral land classification of El Dorado County, California: California Geological Survey Open-File Report 2000-03.
Noble, D. (2002), Mines of El Dorado County: El Dorado County Library website: http://www.eldoradolibrary.org/mines.htm
USGS (2005), Mineral Resources Data System (MRDS): U.S. Geological Survey, Reston, Virginia, loc. file ID #10310666.
California Geological Survey Mineral Resources files, Sacramento, California, file No. 322-5969.
California Geological Survey Mineral Resources files, Sacramento, California, file No. 331-7174.
California Geological Survey Mineral Resources files, Sacramento, California, file No. 332-0454.
California Geological Survey Mineral Resources files, Sacramento, California, file No. 332-0489.
California Geological Survey Mineral Resources files, Sacramento, California, file No. 322-5962.
California Geological Survey Mineral Resources files, Sacramento, California, files No. 331-5009.
California Geological Survey Mineral Resources files, Sacramento, California, files No. 331-7169.
California Geological Survey Mineral Resources files, Sacramento, California, files No. 339-8844.
California Geological Survey Mineral Resources files, Sacramento, California, files No. 339-8854.

USGS MRDS Record:10310666

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