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Martinez Gold Mine (Martinez Mine; Martinez Hillside group; Bismark claim; Gold reef claim; Hillside Extension claim; Hillside Extension No. 3 claim; Martinez claim), Logtown, El Dorado District, Mother Lode Belt, El Dorado Co., California, USA

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Latitude & Longitude (WGS84): 38° 38' 12'' North , 120° 49' 6'' West
Latitude & Longitude (decimal): 38.6366666667, -120.818333333

A former lode Au-Pb-Mn mine(s)/mine group located in sec. 12 & in the NE¼ sec. 13, T9N, R10E, MDM, about 2.65 km ESE of Logtown (site), along Martinez Creek (S of the Union Mine; about 4½ miles SE of El Dorado). Discovered in 1942. The property consists of numerous claims but the literature varies widely on the names which it includes. Apparently holdings include the Bismark, Gold Reef, Hillside Extension and Hillside Extension No. 3 and the Martinez claims. Possibly includes other claims as reference shows area of 132 acres . The holdings were 96 acres. Operated by the Hillside Gold Mining Co. in 1915. Owned by the Martinez Gold Mine Co., California (1974). Operated in 1915, 1926 to 1931, and 1934 to 1941. Production years were 1926 to 1931 and 1934 to 1941. MRDS database stated accuracy for this location is 1,000 meters. Worked on a small scale around 1926 and again during the early 1930's. In 1937 some development work was done on the lower workings and a small amount of ore was produced.

NOTE: USGS MRDS files #10029874 & 10101080 present this locality as either a Au or a Au-Pb mine. MRDS file #10095088 presents it as a Mn mine located near the Au mine. Finally, MRDS file #10284672 presents it as a Au-Mn mine. The deposits present are apparently closely situated and are on the same large area under claim.

Mineralization is hosted in rocks of the Mariposa Formation (amphibolite & slate). The ore body (Mn) strikes N5E, dips 60W at a thickness of 0.91 meter and a length of 3.05 meter. The ore (Mn) consists of schist and slate. The veins (Au) are associated with narrow bands of amphibolite and serpentine. Local rocks include Jurassic marine rocks, unit 1 (Western Sierra Nevada and Western Klamath Mountains).

Rhodonite is partially altered to psilomelane and pyrolusite in lenses cut by numerous quartz veins (3 to 6 inches [7.5 to 15 cm] thick). Two lenses are exposed at the site surrounded with sericite schist, being 3 feet thick, 10 and 5 feet long. Fe oxides are associated with the Mn in one lens. The ore runs 20 to 30% Mn and is very high in silica. The country rock is chert and schist.

Local geologic structures include rocks in the area trending NW. Formations are significantly disturbed by faulting. Some are faulted to the NE with displacement from 16 to 30 feet.

Workings include surface and underground openings with a length of 822.96 meters. A 600 foot crosscut adit was driven with numerous raises and drifts. Another 600 foot crosscut adit was driven S of this, and on the hill above, are a number of older workings. The main adit is 1,700 feet N drift adit and 700 foot N drift adit 300 feet above the main adit, both connected by a raise. A 42 foot shaft is near the main adit portal.

Production data (Au) are found in: Clark, Wm. B. & D.W. Carlson (1956)

Analytical data results (Au): Ore during the period 1928 to 1931 yielded $1.80 to $6.40 (period values) Au/ton. Other small tonnages milled from 1923 to 1926 varied from $4.00 to $80 (period values) per ton. Ore yielded in 1917 yielded $4.12 (period values) per ton.

Analytical data results (Mn): The ore grade was 20 to 30% Mn.

Mineral List

7 valid minerals.

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Logan, Clarence August (1926), El Dorado County: California Mining Bureau. (Report 22): 22: 430.

Logan, Clarence August (1934), Mother Lode Gold Belt of California: California Division Mines Bulletin 108, 221 pp.: 30-31, Pl. II.

Logan, Clarence August (1938), Mineral resources of El Dorado County: California Journal of Mines and Geology, California Division Mines (Report 34): 34(3): 237-238, 264, Pl. II.

Trask, Parker Davies (1950) Geologic description of the manganese deposits of California. California Division of Mines Bulletin 152, 378 pp.: 52.

Clark, Wm. B. & D.W. Carlson (1956), Mines and mineral resources of El Dorado County, California: California Journal of Mines and Geology: 52(4): 419, 517, 575, Pl. 10.

USGS (2005), Mineral Resources Data System (MRDS): U.S. Geological Survey, Reston, Virginia, loc. file ID #10029874, 10095088, 10101080 & 10284672.

U.S. Bureau of Mines, Minerals Availability System (MAS) file #0060170005.

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