Colemanite

Borate mineral, hydrated calcium borate (Ca2B6O11�5H2O) that was the principal source of borax until the 1930s. It typically occurs as colourless, brilliant crystals and masses in Tertiary sediments (those formed 66.4 to 1.6 million years ago), where it has been derived from ulexite and borax. The chief localities are the Kramer district, Death Valley, and Daggett, Calif. Colemanite is an