Mary Harrison Mine, Mary Harrison group, Coulterville, Coulterville District, Mother Lode Belt, Mariposa Co., California, USA
|Latitude & Longitude (WGS84):||37° 42' 31'' North , 120° 11' 53'' West|
|Latitude & Longitude (decimal):||37.70861,-120.19806|
A former Au mine located in sec. 3, in the NE¼NE¼ sec. 10, and in sec. 11, T3S, R16E, MDM, 0.2 km (800 feet) SSW of Coulterville (1 mile S of Coulterville on highway 49). Discovered in 1852. Operated during the periods 1852-1887, 1878-1894, and 1897-1904. MRDS database stated accuracy for this location is 1,000 meters.
Mineralization is a vein deposit in a thrust fault fissure, hosted in Late Jurassic slate, serpentinite, greenstone and schist. The ore body strikes N50W and dips 60-75NE at a thickness of 6.1 meters and a width of 30.48 meters. Controls for ore emplacement included the footwall side of a quartz sheet. Black slate is one of the host rocks. The greenstone was derived from pyroxene andesite of Paleozoic Calaveras Formation from the hanging wall. The footwall slate is probably part of the Upper Jurassic Mariposa Formation. The Mary Harrison vein is traceable from the county line on the N to the Virginia Mine of the S. It is characterized by a prominent sheet of massive milky quartz 4 to 290 feet thick between irregular, ribboned masses of quartz-mariposite-pyrite rock, the upper parts of which are commonly converted to porous, earthy masses of yellowish brown iron and silica oxides. Alteration is local and is oxidation by H2SO4. Local rocks include Jurassic marine rocks, unit 1 (Western Sierra Nevada and Western Klamath Mountains).
Workings include underground openings with a total length of 2,133.6 meters and an overall depth of 365.76 meters. They are comprised of a 1,200 foot vertical shaft with levels at 100 foot intervals. A second inclined shaft has levels at 100 foot intervals. There is also a ventilation shaft and more than 5,000 feet of drifts.
Production data are found in: Bowen & Gray (1957).
Production information: Between $330,000 and $400,000 (period values) of Au were produced between 1895 & 1903 at $5 Au/ton in 1897.
5 valid minerals.
Rock Types Recorded
Select Rock List TypeAlphabetical List Tree Diagram
Entries shown in red are rocks recorded for this region.
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
|Mesozoic - Paleozoic|
66 - 541 Ma
|Undivided pre-Cenozoic metavolcanic rocks, unit 2 (undivided)|
Age: Phanerozoic (66 - 541 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. 
Castello, W.O. (1921), Mines and Mineral Resources of Mariposa County: California Mining Bureau; 17th Report of the State Geologist: 124-125.
Laizure, Clyde McK (1928), Mariposa, Madera Counties: California Mining Bureau. Report 24: 100.
Knopf, Adolf (1929), The Mother Lode system of California: USGS PP 157, 88 pp.; […(abstract): Engineering & Mining Journal: 128: 24 (1929); …Geol. Zentralbl., Band 41: (1930)]: 35, 36, 40.
Logan, Clarence August (1934), Mother Lode gold belt of California: California Division Mines Bulletin 108, 221 pp.: 185.
Bowen, O.E., Jr. & C.H. Gray, Jr. (1957), Mines and mineral deposits of Mariposa County, California: California Journal of Mines and Geology: 53(1-2): 130-132, 202.
Murdoch, Joseph & Robert W. Webb (1966), Minerals of California, Centennial Volume (1866-1966): California Division Mines & Geology Bulletin 189: 335.
Pemberton, H. Earl (1983), Minerals of California; Van Nostrand Reinholt Press: 169, 220-221.
USGS (2005), Mineral Resources Data System (MRDS): U.S. Geological Survey, Reston, Virginia, loc. file ID #10030851, 10110792, 10261062.
U.S. Bureau of Mines, Minerals Availability System (MAS) file ID #0060430063.