Branch Mine (Del Oro; El Oro; Branch; Four Brothers; Whatnot), Silver Mountain, Oro Grande District, San Bernardino Co., California, USA
|Latitude & Longitude (WGS84):||34° 39' 4'' North , 117° 16' 15'' West|
|Latitude & Longitude (decimal):||34.65111,-117.27083|
|Köppen climate type:||BSk : Cold semi-arid (steppe) climate|
A former lode Au-Ag-Cu-Pb occurrence/mine located in the S½NW¼ and N½SW¼ sec. 35, T7N, R4W, SBM, 0.3 km (0.2 mile) W of Silver Mountain (summit) (coordinates of record), on the western slope of the mountain, on private land. Operated during the 1880's, 1896 and 1909. MRDS database stated accuracy for this location is 10 meters.
Mineralization is hosted in Late Triassic metavolcanic rock. The ore body strikes N10W and dips 90 at a thickness of 0.3 meter. The vein is 1 foot thick. Locally the wall rocks contain pyrite and the minor ore minerals. Local rocks include Mesozoic volcanic rocks, unit 3 (Mojave Desert, Death Valley area, and Eastern Sierra Nevada).
Workings include underground openings comprised of a 300 foot adit with 2 130 foot raises to surface and several winzes below 200 feet.
Production data are found in: Southern Pacific Company (1964b); Bowen, O.E., Jr. (1954).
Production statistics: Year: 1889 (accurate): 2.89 ounces (82 grams) Au & 21.5 ounces (607 grams) Ag/ton. No other production records were found. Total production may have been between $19,000 and $20,000.
3 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 volcanic rocks, unit 3 (Mojave Desert, Death Valley area, and Eastern Sierra Nevada)|
Age: Mesozoic (66 - 252.17 Ma)
Description: Undivided Mesozoic volcanic and metavolcanic rocks. Andesite and rhyolite flow rocks, greenstone, volcanic breccia and other pyroclastic rocks; in part strongly metamorphosed. Includes volcanic rocks of Franciscan Complex: basaltic pillow lava, diabase, greenstone, and minor pyroclastic rocks.
Comments: Southeastern California and eastern Sierra Nevada. Mostly rhyolitic to dacitic ignimbrites and tuffs. Includes andesite, basalt, pyroclastic rocks, and sedimentary rocks. In part strongly metamorphosed. Continental and marine
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. 
Bowen, O.E., Jr. (1954), Geology and mineral deposits of Barstow quadrangle, San Bernardino County, California: California Division Mines Bulletin 165: 130.
Southern Pacific Company (1964b) Minerals for Industry, Summary of Geological Survey 1955 - 1961: Vol III - 242 pp., Southern California, Southern Pacific Co., San Francisco, CA 94105: 49.
USGS (2005), Mineral Resources Data System (MRDS): U.S. Geological Survey, Reston, Virginia, loc. file ID #10035601 & 10164327.
U.S. Bureau of Mines, Minerals Availability System (MAS) file #0060710075.