Colorless prismatic crystals of the very rare Pb borate mineral leucostaurite from the TL (Asunción Mine, Caracoles, Sierra Gorda, Antofagasta Province, Antofagasta Region, Chile) and only one of three known localities worldwide. Ex. Erich Laskowski collection (USA). — Photo: David Hospital · CC BY 4.0
Leucostaurite
Leucostaurite is an IMA-recognized mineral species in the borate class, with the chemical formula Pb₂[B₅O₉]Cl·0.5H₂O.
It crystallizes in the orthorhombic crystal system (space group Pnn2). It is a member of the Hilgardite structural group.
Key properties: Mohs hardness 4; specific gravity 5.071; White streak; Adamantine luster.
IMA symbol Lsr, IMA status: approved, named in 2007.
A secondary mineral by the interaction of evaporitic brines within the oxidation zone of a base-metal deposit.
It is found associated with Boleite, paralaurionite, caracolite, bindheimite, gypsum, penfieldite, challacolloite, schwartzembergite, cesanite, seeligerite.
Its name comes from the Greek “leukos” (white) and “stauros” (cross) in allusion to the white or transparent, colorless cruciform twinned crystals.