probertite

Probertite is a rare borate mineral with the chemical formula NaCaB5O7(OH)·3H2O. It is a hydrated sodium calcium borate hydroxide. It typically occurs as fine-grained, chalky white masses or as delicate, acicular crystals. The mineral is translucent to opaque. Probertite was first described in 1975 from samples found in the Searles Lake area of California, USA. It is named in honor of Dr. F. Probert, a notable mineral collector. In addition to its type locality in California, probertite has also been found in other borate-rich deposits around the world, including in Argentina and Chile. It is often associated with other borate minerals such as ulexite and colemanite. Probertite forms in arid environments through the evaporation of boron-rich brines. Its rarity and specific geological conditions for formation make it of interest to mineral collectors and geologists studying evaporite deposits. The mineral is not of significant economic importance.