Colemanite

specimen number:
2354164

location:
Kramer Deposit, Boron, Kern Co., California, USA

description:
Lustrous colorless bladed crystals of colemanite to 1.0 cm in size on matrix. In good condition.

The Kramer Deposit in Boron, Kern County, California, is one of the largest and richest borate deposits in the world, formed during the Miocene Epoch as volcanic and geothermal waters filled an ancient lake basin surrounded by desert terrain. Mining operations began in the late 1920s following the discovery of buried borate beds, transforming the area from underground shaft workings into a massive open-pit mine operated by the Pacific Coast Borax Company and its successors. High-grade lacustrine sedimentary layers within the deposit contain abundant borate mineralization, including colemanite, a hydrated calcium borate mineral that forms clear to white monoclinic prismatic crystals and radiating crystalline masses within the lake-bed claystones. Collectors and mineralogists value colemanite specimens from the locality for their exceptional crystal luster, size, and sharp form, though collecting access today is strictly managed by active mining operations.

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