Colemanite

Colemanite is a hydrated calcium borate mineral with the chemical formula Ca2B6O11·5H2O. It belongs to the borate minerals and forms in evaporite environments where boron-rich fluids evaporate and precipitate minerals.

Colemanite typically occurs as tabular to prismatic crystals or in compact masses. Its color ranges from colorless to white, with possible yellowish or brown tints. The mineral has a vitreous to pearly luster and is relatively soft. It is stable at surface conditions but loses water upon heating, shifting to less hydrated borates.

In terms of occurrence, colemanite is found worldwide with notable deposits in Turkey and in the western United States, including California and Nevada. It commonly occurs alongside other borates such as borax and ulexite in evaporite sequences.

Colemanite is an important ore of boron. It is processed to produce boric acid and a range of borate products used in glass and ceramics manufacture, agriculture as a micronutrient, and various chemical applications. The mineral was named after the Coleman Mine in California, where it was first described.