Picacho
Mine is located near the bend of the Colorado River north of Yuma
Arizona, and named after the nearby Picacho Peak, an obelisk-shaped
mountain rising 1,947 feet above the desert floor. The mine was
opened by Mexican placer miners after 1852, the gold mines expanded
into hard rock quarrying by 1872. Picacho employed 700 miners at
its peak from 1895 to 1900. Mill accidents, low ore quality, and
the loss of cheap river transport with the building of Laguna Dam
led to numerous periods of inactivity. The most productive period
was at the Picacho Basin Quartz Mine about five miles south of the
village, where from 1904-1910 approximately 30 claims produced
about $2 million on gold.
With ores far from worked out, the Picacho Mines, using modern
techniques, again resumed operations in 1984. The mine had been
reopened as an open pit heap-leach operation by Glamis Gold in 1981
and was mined up until 1998. Gold production ceased in 2000. Glamis
Gold produced 10.5 t of gold from the Picacho Mine during its 20
years of operation. Heap leaching may continue for the next few
years.
The gold deposit is in a nearly flat-lying
fault of probable Oligocene age. The deposit of gold is found in
Mesozoic schists, granites, and gneiss that were derived from those
rocks. They are often overlain by unmineralized late Oligocene
volcanic rocks. The Picacho deposit is characterized by a
gold-arsenic-antimony geochemical signature consistent with
bisulfide complexing of gold in reducing fluid. These post-ore
faults are associated with red earthy hematite precipitation,
pyrite oxidation, and supergene enrichment of gold.
TO LOG THIS
CACHE:
1) Find some of the
Picacho "Breccia" just east of these coordinates. What color is it?
Why is it this color?
To log this cache e-mail me
the
answer
HERE
.
REFERENCES:
Richard, Stephen M. and Spencer, Jon E. Geologic map
of the Picacho mine area, southeastern California. Scale 1:10,000.
Arizona Geological Survey open file report 96-30, pub. 1996. OCLC
#37324717
Steven Losh, Dan Purvance, Ross Sherlock, E.
Craig Jowett. 2005. Geologic and geochemical study of the Picacho
gold mine, California: gold in a low-angle normal fault
environment. Mineralium Deposita, 140, 137-155.