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Rainbow Mine, 16 to 1 Mine (Sixteen-to-One Mine; Original Sixteen-to-One Mine), Alleghany, Alleghany District (Forest District), Sierra Co., California, USA

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Latitude & Longitude (WGS84): 39° 27' 24'' North , 120° 50' 7'' West
Latitude & Longitude (decimal): 39.4566666667, -120.835277778
A former lode Au occurrence/mine located in the N½ (estimated) secs. 2 & 3, T18N, R10E, MDM, about 2 km SSE of Alleghany, on National Forest land. MRDS database stated accuracy for this location is 100 meters. This claim/mine was acquired by the Sixteen-to-One Mine during the WWII period.

Mineralization is a Au vein 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 conglomerate, slate, chert, gabbro, schist, and amphibolite. The ore body strikes NW and dips NE at a thickness of 1.83 meters. Local alteration includes carbonitization. Local rocks include undivided pre-Cenozoic metavolcanic rocks, unit 2 (undivided).

Three vein occur of the same age. The Rainbow and barren veins are parallel. The Clinton vein strikes N and dips steeply W and limits the other two. The veins are cut by serpentine and gabbro dike(s). Chlortized amphibolite schist hanging wall has been altered to mariposite, siderite and ankerite. Schit drag implies reverse faulting with unknown displacement. The wallrock is often black, pebbly slate. Serpentine dike & in groves adit footwall (??). The Rainbow vein strikes N75-80W in the upper workings, N45-55W in the lower workings, dips 20-70NE, steeper above. Average thickness of the vein is no more than 2 feet with quartz lacking in places. It is continuous for 1,400 feet. A parallel vein lies in the hanging wall of the Rainbow vein, 100 feet E. It is continuous, thin, for 150 feet. The Clinton or North group of veins, separated in places by several feet of country rock, strikes N8W and dips steeply W. Its fissuring faults the Rainbow system, though filling is contemporaneous. Possibly fissuring faded out against the serpentine dike to the S. A N projection to the Rainbow Extension is possible. Fault movement in different directions at different times make the vein junction region complex. Fissuring & folding later than the vein but prior to Au introduction is shown. Post-mineralization movement along & in veins is evident. Green schist, probably altered tuff, forms the footwall but not well enough exposed to determine fault displacement, which probably wasn't large, less than 100 feet. Altered carbonate-mariposite type wallrock with ankerite-mariposite green banding and siderite or Fe-rich ankerite brown banding more prominent in green schist than black slate. Slickenside-plated pyrite of supergene origin (?) is present. The Rainbow vein is lost to the E in stringers which steepen and follow the slate cleavage.

The RAinbow vein has yielded nearly all production. High-grade ore is associated with coarse arsenopyrite near serpentine. Small shoots of exceedingly rich ore occur in the Clinton or North vein group. Practically all production was from the junction of the Rainbow & Clinton veins. Gold also occurs in flakes in gougy slip of presumed inter-mineral age. High-grade ore possibly occurs on the 2 lowest levels, and in the northerly extension of the parallel vein. Ground between the E end of the Rainbow workings, and workings of the Oriflamme, Irelan & Arcade Mines is unexplored.

Workings include surface and underground openings with an overall depth of 243.84 meters. Winzes were sunk from the gravel adit. Long crosscut Groves tunnel 1,400 feet. The lower adit with inclined shaft on the vein.

Production data are found in: Ferguson, Henry G. & R.W. Gannett (1932).

The Rainbow vein yielded all but $50,000 of the production. Before 1884 as much as $60,000 (period values) was taken out in a single day and $100,000 (period values)/month. A single specimen exhibited in San Francisco contained $20,468 (period values) of Au. Ferguson gives $145/foot ratio for the Rainbow, $22/foot for the Clinton.

Mineral List

13 entries listed. 10 valid minerals.

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Ferguson, Henry G. & R.W. Gannett (1929), Gold quartz veins of the Alleghany district, California: A.I.M.E. Technical Publication 211 (class 1 Mining geology 24); […Mining & Metallurgy: 10: 252 (1929)]: 30.

Ferguson, Henry G. & R.W. Gannett (1932), Gold quartz veins of the Alleghany district, California: USGS Professional Paper 172: 102-105.

Averill, Charles V. (1942a), Mineral resources of Sierra County: California Journal of Mines and Geology, California Division Mines (Report 38): 38(1): 63.

McCulloch, W.C., Oesterling, W.A., Spurck, W.H., & Tischler, M.S. (1964), Minerals for Industry, Northern California, Southern Pacific Company: Vol. II: 35-36.

Murdoch, Joseph & Robert W. Webb (1966), Minerals of California, Centennial Volume (1866-1966): California Division Mines & Geology Bulletin 189: 232, 256.

Pemberton, H. Earl (1983), Minerals of California; Van Nostrand Reinholt Press: 137, 427.

USGS (2005), Mineral Resources Data System (MRDS): U.S. Geological Survey, Reston, Virginia, loc. file ID #10086510 & 10165438.

U.S. Bureau of Mines, Minerals Availability System (MAS) file #0060910124.

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