Home > California Borate Minerals – July 22 > MS0971 Colemanite

Colemanite - Sold

Colemanite is a calcium borate mineral. In 1883, Henry Hanks, the first state mineralogist of California, published an early announcement of the mineral. 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 excellent specimen showing a round knob of crystals. Most crystals occur in narrow cavities, so such convex specimens are quite unusual. The mineral here forms white bladed crystals to 1.2 cm, in a convoluted shape. Quite appealling!