Home > California Borate Minerals – July 22 > MS0973 Colemanite, Orpiment

Colemanite, Orpiment - Sold

Colemanite is a calcium borate mineral. In 1883, Henry Hanks, the first state mineralogist of California, published an early notice of the mineral colemanite. The mineral name honors William T.Coleman (1824-1893), early developer of the borate industry in California. At this locality, mining operations stockpile colemanite since it is easier to process sodium borate ores. Colemanite is a stable mineral, in dry and humid environments. This is an interesting association specimen of small colemanite crystals to 4 mm including powdery orpiment. Recent studies indicate colemanite can absorb some parts per thousand arsenic. An interesting association piece, with great color. Quite appealling!