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Formula: Na2B5O7(OH)3.2H2O
Hydrated pentaborate
Crystal system: Triclinic
Specific gravity: 2.053 measured, 2.049 calculated
Hardness: 3 to 3½
Streak: White
Colour: Colourless
Solubility: Soluble in water, easily soluble in acids
Environments
Localities
At the type locality, the Tincalayu Mine, Antofagasta de la Sierra Department, Catamarca Province, Argentina,
ezcurrite occurs in cleavable masses that have a bladed fibrous structure, sometimes radiating; masses are up
to 7 cm long and 1.5 cm wide. When heated it swells to an opaque white mass, then fuses to a clear glass.
It is colourless and transparent, with a vitreous to satiny lustre. There are two cleavages, one
perfect, one less so. Ezcurrite occurs at the Tincalayu borax mine associated with
borax and kernite.
Ulexite and inderite occur
elsewhere in the deposit
(AM 42.919-921).
Ezcurrite probably formed from solutions derived from dehydration of
borax in a discordant deposit in folded playa
siltstones and
sandstones
(HOM).
Ezcurrite from the Tincalayu Mine -
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