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Kramer Borate Deposit Earthcache

A cache by TerryDad2 adopted by f0t0m0m Send Message to Owner Message this owner
Hidden : 8/15/2005
1 out of 5
1 out of 5

Size: Size: not chosen (not chosen)

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Geocache Description:

The boron open pit mine is located about 3 miles north of the town of Boron. It mines one of the biggest and richest deposits of borax in the world. The visitor Center is open 7 days a week form 9 AM to 5 PM.

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 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 :

  1. The text "GCQ5FV Kramer Borate Deposit Earthcache" on the first line
  2. The number of people in your group.
  3. How the Egyptians used borite.
  4. Sign the guest book in the visitor center noting that you are earthcaching
  5. 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
Quaternary alluvium
Miocene Kramer beds
Arkose member
Shale member (contains the ore body)
Saddleback basalt member
Miocene tuffs, tuffaceous shales, limestone, arkose and conglomerate

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.

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Svaq gur qvfcynl jvgu gur inevbhf zvarenyf bs obeba.

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