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Grand National Mining Company Mine (Tangle Blue Mine), Tangle Blue Lake, Scott Mts, Klamath Mts, Trinity Co., California, USA

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A former lode Au mine located in the SE¼NE¼ sec. 25, T39N, R8W, MDM, 1.5 km (5,000 feet) ENE of Tangle Blue Lake (coordinates of record), on the divide between Tangle Blue Creek and its tributary, Horse Creek, on Bureau of Land Management wilderness land (Trinity Alps Wilderness). Owned by Ezra E. Erich, French Gulch, California (1972). MRDS database stated accuracy for this location is 100 meters.

Mineralization is hosted in granodiorite, hornblendite and diorite. The ore body dips 90 (vertically), at a thickness of 1.22 meters. Ore controls included shearing planes in the host rock. Hanging wall in the drift to the N of the main adit, is a shear zone formed by hornblende diorite. Local rocks include Mesozoic granitic rocks, unit 5 (Klamath Mountains).

Workings include underground openings. The main adit was driven E for 700 feet on a 4 foot thick vein, then strikes the shear zone. A stope 100 foot long, 15 foot wide with a 60 foot face is situated above the adit level. Drifts on the main level, shear zone level, total 300 feet in length. A 100 foot crosscut was driven into the shear zone at 400 feet of depth. Also, a 50 foot deep winze was sunk below adit level on the shear zone. A short shoot of good ore was stoped from this to the main level.

Production data are found in: Averill (1937).

Production statistics: Year 1937 (period 1934 - 1937): 1,500 ounces Au, 2,200 ounces Ag and 1,900 pounds Cu. The shear zone was being mined for Au in 1937. No specific production record wasd found.

Analytical data results: Diorite in the shear zone assayed $3.50/ton in Au.

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Averill, Charles V. (1941), Mineral resources of Trinity County: California Journal of Mines and Geology, California Division Mines (Report 37): 37(1): 38.

McCulloch, W.C., Oesterling, W.A., Spurck, W.H., & Tischler, M.S. (1964), Minerals for Industry, Northern California, Southern Pacific Company: Vol. II: 135.

Hotz, Preston Enslow, Thurber, H.K., Marks, L.Y., and Evans, R.K. (1972), Mineral resources of the Salmon-Trinity Alps Primitive Area, California: U.S. Geological Survey Bulletin 1371-B, 267 pp.: 150.

USGS (2005), Mineral Resources Data System (MRDS): U.S. Geological Survey, Reston, Virginia, loc. file ID #10106546 & 10287772.

U.S. Bureau of Mines, Minerals Availability System (MAS) file ID #0061050185.

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