Oriental Mine (Alta Mine), 16 to 1 Mine (Sixteen-to-One Mine; Original Sixteen-to-One Mine), Alleghany, Alleghany District (Forest District), Sierra Co., California, USA
|Latitude & Longitude (WGS84):||39° 27' 37'' North , 120° 51' 28'' West|
|Latitude & Longitude (decimal):||39.46028,-120.85778|
A former lode Au-Ag-Pt occurrence/mine located in sec. 4, T18N, R10E, and in sec. 33, T19N, R10E, MDM, about 2 km (1.2 miles) SW of Alleghany, along the N canyon wall of Kanake Creek, on private (patented) land within a National Forest area. Discovered and first produced in 1865. Owned/operated by the Dickey Exploration Company (100%), California (1974). MRDS database stated accuracy for this location is 100 meters. The property is an intermittent producer. There was activity at the mine in 1977. Water, electrical power and roads exist at the site for the sole purpose of mining operations, but are inadequate for a larger operation.
Mineralization is a vein Au deposit (Mineral occurrence model information: Model code: 273; USGS model code: 36a; Deposit model name: Low-sulfide Au-quartz vein; Mark3 model number: 27), hosted in quartzite. The ore body strikes N77W and dips 39N at a thickness of 3 meters and a depth-to-top (depth-to-bottom ??) of 305 meters, width of 610 meters and a length of 385 meters. Ore body No. 1 is tabular in a shear zone. Ore body No.2 is massive in a fissure vein. Ore body No. 3 is an irregular replacement body. The primary mode of origin was hydrothermal and the secondary mode was contact metasomatism. Primary ore control was faulting and the secondary control was igneous activity. Wallrock alteration is moderate (propylitic & silicification). Local alteration includes carbonitization and albitic alteration. The oldest rock is schistose quartzite, which grades into fine-grained mica schist with thin quartzite bands. Quartzite is not found in underground workings. Local rocks include Mesozoic gabbroic rocks, unit 2 (undivided).
The vein was productive wherever serpentine contact was explored. The most productive area was a narrow band of gabbro between granite and serpentine. A new ore body was discovered in 1952. Veins consist of branches and stringers with the greatest thickness on the 7th and 8th levels. The vein displaces a porous granite dike about 160 feet horizontally and 200 feet down dip. The dike is 50 feet thick in the upper workings and 350 feet thick in the lower workings.. The granite is coarse, up to ICM+. The feldspar in gabbro is unrecognizable and the augite is almost completely altered to hornblende. Minor thrusting occurred during and after mineralization. The Alta workings are 500 feet SSE of the Oriental shaft. Dumps there contain coarsely crystalline arsenopyrite and pyrite. Veins at the 2 mines may unite in broken ground above the 5th level.
Workings include surface and underground openings with a length of 4,847 meters and an overall depth of 237.74 meters and comprised of a 4,150 foot adit and raise that intersects an inclined shaft on the vein. There are 10 levels with short drifting on each. The Alta workings are caved.
Production data are found in: Ferguson, Henry G. & R.W. Gannett (1932) & Averill, Charles V. (1942a).
Detailed production statistics year by year are provided in USGS MRDS file #10116707.
Ore ran as high as $1000/ton (period values). Pt was detected in native Au samples up to 86.4 parts per million, averaging 32 parts per million. Reportedly $734,000 (period values) of Au was obtained from area on a vein 14 by 22 feet (?).
13 valid minerals.
This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.
Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org
|Cretaceous - Triassic|
66 - 252.17 Ma
|Mesozoic gabbroic rocks, unit 2 (undivided)|
Age: Mesozoic (66 - 252.17 Ma)
Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052. 
MacBoyle, Errol (1920b), Mines and mineral resources of Sierra County: California Mining Bureau. Report 16, 144 pp. (published as separate chapter): 53-54.
Logan, Clarence August (1922), Quartz mining in the Alleghany district: 18th Report of the California Mining Bureau. (Report 18): 18: 511.
Ferguson, Henry G. & R.W. Gannett (1932), Gold quartz veins of the Alleghany district, California: USGS Professional Paper 172: 45, 48, 98-101.
Averill, Charles V. (1942a), Mineral resources of Sierra County: California Journal of Mines and Geology, California Division Mines (Report 38): 38(1): 7-67.
Carlson, D.W. & W.B. Clark (1956), Lode gold mines of the Alleghany-Downieville area, Sierra County, California: California Journal of Mines and Geology: 52: 237-272.
McCulloch, W.C., Oesterling, W.A., Spurck, W.H., & Tischler, M.S. (1964), Minerals for Industry, Northern California, Southern Pacific Company: Vol. II: 37. (reprint: California Division of Mines and Geology Special Publication 94, 1987).
Clark, Wm. B. (1970a) Gold districts of California: California Division Mines & Geology Bulletin 193: 19.
Coveney, Raymond M. & W.C. Kelly (1971), Dawsonite as a daughter mineral in hydrothermal fluid inclusions: Contributions to Mineralogy and Petrology: 32: 334-342, 335.
Coveney, Raymond M. (1981) Gold quartz veins and auriferous granite at the Oriental Mine, Alleghany District, California. Economic Geology and the Bulletin of the Society of Economic Geologists (December 1981), 76(8):2176-2199
Bohlke, J.K. (1982), Written communication to N.J. Page, USGS.
Pemberton, H. Earl (1983), Minerals of California; Van Nostrand Reinholt Press: 33, 171, 198.
USGS (2005), Mineral Resources Data System (MRDS): U.S. Geological Survey, Reston, Virginia, loc. file ID #10086500 & 10116707.
U.S. Bureau of Mines, Minerals Availability System (MAS) file #0060910001.
Mine Safety and Health Administration (MSHA), MSHA file No. 0400898.