Afterthought

The Afterthought is a copper mine located in Shasta county, California at an elevation of 1,801 feet.

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.

Site Name

Primary: Afterthought
Secondary: Copper Hill

Commodity

Primary: Copper
Secondary: Gold
Secondary: Silver
Secondary: Lead

Location

State: California
County: Shasta
District: East Shasta Copper - Zinc

Land Status

Land ownership: National Forest
Note: the land ownership field only identifies whether the area the mine is in is generally on public lands like Forest Service or BLM land, or if it is in an area that is generally private property. It does not definitively identify property status, nor does it indicate claim status or whether an area is open to prospecting. Always respect private property.

Holdings

Not available

Workings

Type: Underground

Ownership

Not available

Production

Year: 1952
Time Period: 1905 - 1952
Material type: CU
Description: Cp_Grade: ^3.23 % Cu, 16.15 % Zn, 2.17 % Pb, 5.55 Oz/Ton Ag, .03 Oz/Ton Au.

Deposit

Record Type: Site
Operation Category: Past Producer
Operation Type: Underground
Year First Production: 1873
Year Last Production: 1952
Discovery Year: 1862
Years of Production:
Organization:
Significant: N
Deposit Size: L

Physiography

General Physiographic Area: Pacific Mountain System
Physiographic Province: Pacific Border Province
Physiographic Section: Klamath Mountains

Mineral Deposit Model

Model Name: Massive sulfide, kuroko

Orebody

Form: LENTICULAR

Structure

Not available

Alterations

Alteration Type: L
Alteration Text: Silicified, Pyritized, Sericite, Carbonatization, Albitization

Rocks

Name: Rhyolite
Role: Host
Age Type: Host Rock Unit
Age Young: Late Jurassic

Name: Rhyolite
Role: Host
Age Type: Associated Rock
Age Young: Late Jurassic

Name: Rhyolite
Role: Host
Age Type: Host Rock
Age Young: Late Jurassic

Analytical Data

Analytical Data: 15 % ZN, 2 % CU, 5 OZ. AG/TON, 2 % PB, AND .03 OZ AU/TON.

Materials

Ore: Galena
Ore: Tetrahedrite
Ore: Tennantite
Ore: Azurite
Ore: Limonite
Ore: Malachite
Ore: Chalcocite
Ore: Bornite
Ore: Chalcopyrite
Ore: Sphalerite
Ore: Covellite
Ore: Pyrite
Ore: Luzonite
Gangue: Barite

Comments

Comment (Deposit): OUTCROPS ARE MARKED BY PROMINENT GOSSANS FIRST PROSPECTED FOR THEIR GOLD CONTENT.

Comment (Workings): OVERALL LENGTH OF 17,200 FEET INCLUDES DRIFTS, CROSSCUTS AND STOPES IN ADDITION TO 2,200 FEET OF SHAFTS, RISES AND WINZES.

Comment (Geology): HOST ROCK IS PROBABLY A RHYOLITE PORPHYRY. ; GEOL.DESC: ALTERED ROCKS CONTAIN SIGNIFICANT QUANTITIES OF ALBITE, SILICA, HYDROUS MICA, CALCITE AND PYRITE. SULFIDE ORE BODIES REPLACE SHEARED HOST ROCKS AT CONTACT. 16 ORE BODIES COMPOSED OF MASSIVE AND BANDED SULFIDES.

Comment (Location): Original coordinates for line#1 were: lat/long NAD27 40-44-10N 122-4-56W (40.73611 -122.08222); UTM N4509475 E578350 Z10N; PLSS line# 1: Meridian- Mount Diablo, TWNSHP 033N, RNG 002W, Sect 10,11,15, Sect_fract . The location was modified by view of workings in Google Earth, which is pretty close to coordinates given in Mosier and others (2009)

References

Reference (Deposit): Mosier, D.L., Berger, V.I., and Singer, D.A., 2009, Volcanogenic massive sulfide deposits of the world; database and grade and tonnage models: U.S. Geological Survey Open-File Report 2009-1034 [http://pubs.usgs.gov/of/2009/1034/].
URL: http://pubs.usgs.gov/of/2009/1034/

Reference (Production): LYDON P. A., AND O'BRIEN, J. C., 1972

Reference (Deposit): STINSON, M. C., 1957 , CALIF. JOURNAL OF MINES AND GEOLOGY, VOL. 53 , PG. 684 .

Reference (Deposit): ALBERS, J. P., AND ROBERTSON, J. F., 1961 , GEOL. AND ORE DEPOSITS OF EAST SHASTA, COPPER - ZINC DISTRICT, SHASTA COUNTY, CAL.: U.S. GEOLOGICAL SURVEY PROF. PAPER 388 , 107 P.

Reference (Deposit): LYDON, P. A., AND O'BRIEN, J. C., 1974 , CALIF. DIV. MINES AND GEOLOGY COUNTY REPT. 6 , SHASTA COUNTY, P. 31 , 104 .

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.