|Latitude & Longitude (WGS84):||38° 40' 58'' North , 119° 41' 57'' West|
|Latitude & Longitude (decimal):||38.68278,-119.69917|
|Köppen climate type:||Csb : Warm-summer Mediterranean climate|
A former lode Au-Cu-Ag-Sb-Pb-Zn-As-baryte mine located in the W½ sec. 29, T10N, R21E, MDM, 1.7 km (5,500 feet) ESE of Mogul Peak and 2.0 km (6,400 feet) N of Loope, along Mogul Gulch (3 miles NW from Heenan Lake), on National Forest land. MRDS database stated accuracy for this location is 100 meters.
Mineralization is hosted in Pliocene andesitic rhyolite. Geologic structures involve a shear zone. Alteration is local (silicification). This deposit is on the E side of the major alteration/silicification of the district. The shear zone appears to trend SW through the Curtz & Georgiana Mines, and then SE along the S side of Monitor Canyon near the Zaca mill. The mine dump has white, silicified rock that contains mostly fine- to medium-grained minerals. The silicified hilltop stands out from surrounding unaltered andesite. The silicified rock is iron oxide-stained in places. This mine resembles other district producers except that enargite is more abundant. Enargite (or other copper-arsenic-antimony sulfosalts) is the most important copper ore mineral (Burchard 1883). A body of enargite mixed with pyrite was found in the late 19th century, measuring 10 to 15 feet thick and 20 to 30 feet long. Local rocks include Tertiary pyroclastic and volcanic mudflow deposits, unit 9 (Cascade Range).
From Wachter (1971): Jasperoid outcrop is mostly quartz and has silver and gold with high trace elements. Hydrothermal alteration at the Morningstar deposit was caused by fluids with a low K+/H+ ratio (orthoclase is almost absent). The "clay" associated with enargite is quartz, kaolinite, and pyrite. The "clay" associated with massive pyrite is quartz with lesser sericite and dickite. Sericitic alteration and quartz-jasperoid present at Morningstar and Mogul Peak.
Also from Wachter (1971): A sample of enargite yielded 16% copper, 50 ounces per ton silver, and 0.5 ounce per ton gold. Similar material showed blebs of an unknown silver mineral in enargite, and possible cylindrite was intergrown with enargite. A sample of porous pyrite (with no other visible sulfides) yielded 0.2% copper, 5 ounces per ton silver, and 0.08 ounce per ton gold.
Workings include underground openings. A 1,200 foot main adit, trending SSE, is known as the 148 foot level. A 480 foot deep shaft connected 922 feetN from the portal. There are also 220, 280 and 480 foot levels. Crosscuts extend to the ore zone. Also stopes and winzes. The main adit & shaft were still open in 1971. Workings of the Georgiana & Curtz Mines were for a time driven for ore bodies in the same zone.
Production data are found in: Clark (1977).
Some enargite ore (carrying $400 (period values) per ton in Cu, Au & Ag) was shipped as far as Swansea, Wales, for smelting. The mine produced fairly steadily during the period 1863 - 1904 on a fairly large scale. Minor exploration was done in 1951, 1952 & 1957.
1882: Over a six month and 16 day period, an average of 3.5 tons of ore per day was processed in the Exchequer mill with the Hunt, Douglass, and Stewart Process. The total output for this period was 70,895 pounds of copper and $18,172 (period values) of Au & Ag.
1901: 22 tons of ore yielded 17% copper, $32.00 (period values) in Au, and 49 ounces of Ag per ton.
25 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
|Gelasian - Chattian|
1.806 - 28.1 Ma
|Tertiary pyroclastic and volcanic mudflow deposits, unit 9 (Cascade Range)|
Age: Cenozoic (1.806 - 28.1 Ma)
Stratigraphic Name: Alturas Formation; Bonta Formation; Cedarville Series; Delleker Formation; Ingalls Formation; Mehrten Formation; Nomlaki Tuff Member; Penman Formation; Reeds Creek Andesite; Spanish Canyon Formation; Tropico Group; Tuscan Formation; Valley Springs Formation
Description: Tertiary pyroclastic and volcanic mudflow deposits.
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. 
66 - 145 Ma
|Mesozoic intrusive rocks|
Age: Cretaceous (66 - 145 Ma)
Lithology: Intrusive igneous rocks
Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529.