COLEMANITE, a hydrous calcium borate found in Cali fornia as monoclinic crystals It contains 5o•9% of boron trioxide, and is an important source of commercial borates and boracic acid. Beautifully developed crystals, up to two or three inches in length, encrust cavities in compact, white colemanite they are colourless and transparent with brilliant lustre. There is a perfect cleavage parallel to the plane of sym metry of the crystals. Hardness 4-42 sp. gr. 2.42. The mineral was first discovered in 1882 in Death Valley, Inyo county, Calif., and in the following year it was found in greater abundance near Daggett, in San Bernardino county, Calif., forming with other bo rates and borosilicates a bed in sedimentary strata of sandstones and clays. Priceite and pandermite are hydrous calcium borates with very nearly the same composition as colemanite.