The Thomas Round Mountain is a manganese mine located in Mendocino county, California.
About the MRDS Data:
All mine locations were obtained from the USGS Mineral Resources Data System. The locations and other information in this database have not been verified for accuracy. It should be assumed that all mines are on private property.
Mine Info
Satelite View
MRDS mine locations are often very general, and in some cases are incorrect. Some mine remains have been covered or removed by modern industrial activity or by development of things like housing. The satellite view offers a quick glimpse as to whether the MRDS location corresponds to visible mine remains.
Thomas Round Mountain MRDS details
Site Name
Primary: Thomas Round Mountain
Commodity
Primary: Manganese
Location
State: California
County: Mendocino
Land Status
Not available
Holdings
Not available
Workings
Not available
Ownership
Not available
Production
Not available
Deposit
Record Type: Site
Operation Category: Producer
Operation Type: Unknown
Years of Production:
Organization:
Significant: N
Deposit Size: L
Physiography
General Physiographic Area: Pacific Mountain System
Physiographic Province: Pacific Border Province
Physiographic Section: California Coast Ranges
Mineral Deposit Model
Not available
Orebody
Not available
Structure
Not available
Alterations
Not available
Rocks
Name: Chert
Role: Host
Age Type: Host Rock
Age Young: Late Cretaceous
Name: Chert
Role: Host
Age Type: Host Rock Unit
Age Young: Late Cretaceous
Analytical Data
Not available
Materials
Ore: Rhodochrosite
Comments
Comment (Production): MINE IS CREDITED WITH PRODUCTION OF 6,230 TONS OF ORE FROM 1914 TO 1918, AVERAGING 50% MANGANESE AND 7 TO 10% SILICA (1,500 TONS MAY HAVE BEEN FROM SOUTH THOMAS MINE). NO PRODUCTION SINCE 1918; MOST ADITS ARE CAVED. IDLE.
Comment (Geology): ORE HOSTED IN FRANCISCAN COMPLEX--L. TO L. ; GEOL.DESC: ORE BODY NEAR TOP OF WELL-BEDDED RED CHERT AND POORLY BEDDED WHITE CHERT. CHERT IS OVERLAIN AND UNDERLAIN BY SANDSTONE. CHERT HAS A GENERAL STRIKE OF N 45 W, AND DIPS 45 TO 80 N. E. AN E. - W. TRANSVERSE FAULT CUTS THE SEQUENCE. MAIN ORE BODY HAS SAME ATTITUDE AS CHERT. SILICEOUS ORE TOWARDS THE BOTTOM OF THE BODY CONTAINS BLACK MANGANESE OXIDES, WITH ABUNDANT CHERT IN CORES AND PATCHES. HIGH GRADE ORE IS NEOTOCITE CUT BY VEINLETS OF RHODOCHROSITE.
Comment (Deposit): MOST OF BLACK OXIDE ORE HAS PROBABLY BEEN MINED BUT FAVORABLE AREAS REMAIN TO BE EXPLORED AND THERE SHOULD BE GOOD CHANCES FOR DEVELOPING LARGE RESERVES OF PRIMARY ORES, PROBABLY NEOTOCITE AND RHODOCHROSITE.
Comment (Workings): OPEN CUTS, ADITS.
References
Reference (Deposit): USBM R.I. 4849, P. 11-14.
Reference (Deposit): CALIF. JOUR. MINES & GEOLOGY, V. 49, NO. 4, OCT. 1953, PP. 364, 391
Reference (Deposit): D.O.M. BULL. 152, PP. 152-145
California Gold
"Where to Find Gold in California" looks at the density of modern placer mining claims along with historical gold mining locations and mining district descriptions to determine areas of high gold discovery potential in California. Read more: Where to Find Gold in California.
