The admission fee is $1 for motorcycles and $2 for cars.
All admission fees are donated to local non-profit
organizations. Additional directions are available at
http://www.borax.com/borax6.html. Thanks to US Borax for
allowing this Earthcache to be placed at its visitor
Center.
The Boron Open Pit Mine is the largest open pit mine in
California and supplies nearly half of the world's borates. Borates
are used in the manufacture of glass, fiberglass, herbicides,
ceramics, soaps and detergents, fluxes, fertilizers, and fire
retardants. Mining operations (not necessarily as an open pit) have
been going on at the site for over 130 years.
From the coordinates you can see the mining activities and pit.
The pit is so deep you can't see the bottom of it, but there is a
good aerial photo of the pit in the visitor center. The borates
begin most of the way down the pit where the earth begins to turn
whitish. So far the mine as been extracting from the shallowest
deposits. Future expansion of the mine will be off to the east and
have to dig even deeper.
The Boron Open Pit Mine mines from the Kramer Borate Deposit.
This deposit was formed in a small nonmarine basin associated with
thermal (volcanic) spring activity during the Miocene. The
formation of the Kramer Borate Deposit began with the creation of a
basin caused by subsidence along the Western Borax Fault, an
east-west trending fault just south of the mine. From the
coordinates, it is between you and the mine and runs east/west. The
area the mine is on decreased in elevation relative to the area the
visitor center is on. Currently there are no easily identifiable
surface features of the fault. This basin was initially partially
filled with a layer of basalt about 19 million years ago. This
basalt is now called the Saddleback Basalt (the red material at the
top of the left side of the figure below).
source: ©2005 Borax. All Rights Reserved
Continued subsidence along the fault maintained a basin that was
filled with surface water and water from hot springs forming a
lake. The water from the hot springs contained high concentrations
of boron. As the water cooled, borax crystals formed on the bottom
of the lake. Seasonal fluctuations in sediment being washed into
the lake and/or long-term changes in flow from the hot springs
created a series of borate rich layers layered in between mud
layers (the green and blue in the figure above). In the hi-grade
zones, borax makes up more than 80% of the material while in the
low-grade zones, borax makes up less than 50% of the material.
Ripple marks, evidence of shallow water, have been found on the top
of some of the layers.
About 16 to 18 million years ago, the lake and hot springs dried
up depositing a final layer of clay that encased the borate
deposit. Continued subsidence along the Western Borax Fault dropped
the borate deposit further down. Erosion in the surrounding area
filled the basin with 2,000 feet of Miocene and Pliocene
sediments.
source: ©2005 Borax. All Rights Reserved
About 6 million years ago, the entire Mojave region began to be
uplifted. During this uplift, a few faults formed through the
deposit and some folding occurred. In addition a large amount of
the Miocene and Pliocene sediments that had been deposited on top
of the borate deposit were eroded away. The combination of uplift
and erosion brought the borate deposits to within 150 feet of the
surface. A final layer of alluvium was deposited in the Quaternary
and Recent times (the yellow on the top of the figure below)
source: ©2005 Borax. All Rights Reserved
Logging requirements:
Send me a note with :
- The text "GCQ5FV Kramer Borate Deposit Earthcache" on the first
line
- The number of people in your group.
- How the Egyptians used borite.
- Sign the guest book in the visitor center noting that you are
earthcaching
- Get your free borax sample.
(The staff usually don't know about the earthcache eventhough the
management approved the cache.)
Post some pictures if you have them.
More Technical Notes: The Kramer ore body contains a varity of
boron containing minerals including, borax, kernite, probertite,
ulexite, and colemanite. These minerals were formed by primary
precipitation and from secondary mineralization under elevated
temperature and pressure. The Kramer deposit is the type locality
for both kernite and probertite.
The Kramer ore body is a roughly lenticular sedimentary sequence
of lacustrine and fluviatile origin. They are a conformable Miocene
sequence between the base of the Quaternary alluvium and the base
of the Saddleback basalt.
A generalized stratigraphic column for the deposit
follows:
Recent alluvium
(unconformity)
Quaternary alluvium
(unconformity)
Miocene Kramer beds
Arkose member
Shale member (contains the ore body)
Saddleback basalt member
(unconformity)
Miocene tuffs, tuffaceous shales, limestone, arkose and
conglomerate
(unconformity)
The following documents were used to generate
this cache:
- Sifke, J.W., The Boron Open Pit
Mine At The Kramer Borate Deposit, The Diversity of Mineral and
Energy Resources Southern California, Guidebook Series Volume 12,
pp. 4-15, 1991, by Society of Economic Geologists. McKibben, M.S.,
ed.
- http://www.borax.com/borax6a.html
-
http://www.borax.com/practices1a.html
-
http://minerals.usgs.gov/minerals/pubs/commodity/boron/120400.pdf
