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California Borate Company property (Western Borax Mine; Western Mine), Kramer Borate deposit, Boron, Kramer District (Kramer Borate District), Kern Co., California, USA

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Latitude & Longitude (WGS84): 35° 2' 4'' North , 117° 40' 32'' West
Latitude & Longitude (decimal): 35.0344444444, -117.675555556
A B (borate) deposit/mine located in sec. 23, T11N, R8W, SBM, 4.6 km (2.8 miles) NNW of Boron.

Im not sure what this mine should be called now because it doesn't exist any more except for perhaps some water filled back filled stopes some hundreds of feet deep slightly to the south of the big open pit borate mine at Boron, California. (Rock Currier 2014)

Here is what Joe Siefke, a retired mine geologist who worked for US Borax Co. at Boron says about it:

To my knowledge no gerstleyite was ever found in the pit (The big open pit mine at Boron).

The Western mine was owned by Mudd, Mudd, Mudd, & Dub, otherwise known as the Kern County Land Co. ( early owners of the Thompson mine in Furnace Creek). The Western passed into the hands of American Potash and thence onto Kerr McGee. (US) Borax bought the Western about 30 years ago from Kerr McGee for $10mm but literally had to get an act of Congress passed to overcome the antitrust consent decree.

The Western shaft was demolished nearly 20 years ago. The pit south rim is now 1/4 mile south of the shaft site. The Western was virtually mined out by 1950 with sand stope filling to maximize recovery. The Western property boundary was a nuisance to Borax; Borax needed the property because 40mm tons of its own reserves were lost if they couldn't be mined by open pit with the pit walls on Western property. Two-thirds of the ores remaining at Boron are kernite, located in the deep southeastern portion of the deposit (stripping ratio ~30:1!). Borax is spending north of $150mm to do process plant construction for the direct feed of kernite to the primary (hot water) process plants.

I drilled several core holes within the Western ore block in attempts to get complete lake bed & ore intercepts by targeting the underground pillars. We missed the pillars in a couple of holes, but still brought up sodium borate mush in the core barrel from what was a kernite ore stope. We concluded that because the workings were flooded from more than 50 years previous, the openings had swollen shut due to hydrating kernite (the Western shafts had static water levels at 300' below surface at the time & the workings were at 800' depth).

Operations at Boron are now known as Rio Tinto Minerals. Boron essentially abandoned separating the calcium borates nearly 20 years ago when they converted to bigger equipment and from 25' to 50' mining faces. Previous Ca stockpiles ran about 11% B2O3. Current stockpiling attempts apparently run about 5%, hopelessly short of any economic separation. The earlier stockpiles contain, I believe about 30mm tons Ca borates, not enough to warrant the expensive processing.

Twenty years ago, Borax produced perhaps 60% of the world's borate products; Today that production may be about 30&. At last count, the Turkish deposit at Kirka contained in excess of 600,000,000 tons of borax, more than 3X the size of the original deposit at Boron. Needless to say, Turkey will control the future of borates. By the way, Bigadic is calcium borates.
(Joe Siefke 2014)

Mineral List

11 entries listed. 11 valid minerals.

The above list contains all mineral locality references listed on mindat.org. This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to visit any sites listed in mindat.org without first ensuring that you have the permission of the land and/or mineral rights holders for access and that you are aware of all safety precautions necessary.


Gale, Hoyt Stoddard (1946), Geology of the Kramer borate district, Kern County, California: California Division Mines Report 42: 332.

Smith, George Irving, Hy Almond, & D.L. Sawyer, Jr. (1958), Sassolite from the Kramer borate district, California: American Mineralogist: 43: 1070, 1074.

Pemberton, H. Earl, Wm. Moller, Jack Schwartz & George Masimer (1960), The minerals of Boron, California, 40 pp. (Published by the Mineral Research Society of California, Montebello, CA): 31, 38.

Murdoch, Joseph & Robert W. Webb (1966), Minerals of California, Centennial Volume (1866-1966): California Division Mines & Geology Bulletin 189: 156, 220, 267, 327, 333, 365.

Morgan, V. and Erd, R.C. (1969) Minerals of the Kramer borate district, California California Division of Mines and Geology Mineral Information Service: 22: 147, 165, 166.

Pemberton, H. Earl (1983), Minerals of California; Van Nostrand Reinholt Press: 137, 238, 276.

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