celandite

Celandite is a rare, hydrated sodium borate mineral with the chemical formula Na₁₈B₁₂Si₂O₃₀·15H₂O. It belongs to the borate mineral group and is notable for its distinctive crystal structure and composition. The mineral was first identified in 1962 by mineralogist Robert A. Hutton, who discovered it in the Boron mining district of Kern County, California, United States. Celandite forms as a secondary mineral in evaporite deposits, often found in arid regions where boron-rich waters evaporate.

Celandite typically occurs as colorless to white, translucent crystals that exhibit a vitreous to pearly luster. Its crystals are often tabular or prismatic, sometimes forming complex intergrowths. The mineral is soft, with a Mohs hardness of approximately 2.5, and has a greasy or soapy feel when touched. It is soluble in water and effervesces when exposed to dilute acids, a characteristic shared with other borate minerals.

The name "celandite" is derived from the type locality, the Coso Range near Boron, California, where it was first described. The mineral is named in honor of the Coso geothermal area, which is rich in boron deposits. Celandite is not commonly found in significant quantities, making it a sought-after specimen among mineral collectors.

Beyond its scientific and collector interest, celandite has limited practical applications due to its rarity and instability in humid conditions. However, its study contributes to the understanding of boron geochemistry and the formation of evaporite deposits. Celandite is classified under the triclinic crystal system and is isostructural with other complex borate minerals like colemanite and ulexite.