Mount Diablo Mine (Mt. Diablo Mine; Diablo Mine; Ryne Mine), Mount Diablo (Mt Diablo), Clayton, Diablo Range, Contra Costa Co., California, USA
|Latitude & Longitude (WGS84):||37° 52' 54'' North , 121° 54' 46'' West|
|Latitude & Longitude (decimal):||37.88167,-121.91278|
|Köppen climate type:||Csb : Warm-summer Mediterranean climate|
A former Hg occurrence/mine located in the SE¼ sec. 29, T1N, R1E, MDM, on the upper E side of Mount Diablo (just E of the summit). Discovered in 1863. Operated by the Nevada Scheelite Company (1956). Owned by the Guadelupe Mining Company. The Mount Diablo Mine and the Ryne Mine were consolidated in 1930. Worked 1875-1877 and again briefly in 1930. Last produced in 1953. MRDS database stated accuracy for this location is 100 meters. Native Americans used the cinnabar in tribal ceremonies. Later the deposit was mined as a placer.
Mineralization is along the contact of a diapir (upthrust plug) of Franciscan sediments and serpentine intruded into sedimentary rocks of the Great Valley sequence. The ore body is irregular and tabular and dips N50E at a thickness of 1.83 meters, a width of 60.96 meters and a length of 39.62 meters. Rhyolite plugs occur nearby. Bituminous clays (Black Alta) also occurs. Local alteration included serpentine converted to silica-carbonate rock. Associated rocks include Late Jurassic-Late Cretaceous rhyolite. Local rocks include Franciscan Complex, unit 1 (Coast Ranges).
Workings include surface and underground openings with a length of 1,219.2 meters and an overall depth of 152.4 meters.
Production statistics: Year: 1962 (period = to 1962): Hg (estimated): ^6 pounds/ton (2,711 grams/metric ton).
Low-grade reserves still exist with 17,000 tons of indicated and inferred reserves.
Commodity ListThis is a list of exploitable or exploited mineral commodities recorded at this locality.
23 valid minerals. 1 (TL) - type locality of 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
|Cretaceous - Jurassic|
66 - 201.3 Ma
|Franciscan Complex, unit 1 (Coast Ranges)|
Age: Mesozoic (66 - 201.3 Ma)
Stratigraphic Name: Franciscan Complex; Dothan Formation; Honda Formation; San Luis Formation; Valentine Spring Formation
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. 
|Late Cretaceous - Jurassic|
66 - 201.3 Ma