Crystal of borax (Na2B4O7) observed with an optical microscopy — Photo: Alessandro e Damiano · CC BY 4.0
Borax
Also known as: Tincal.
The famous hydrated sodium borate — mined from dry lake beds and used for centuries in cleaning, flux and glass-making.
Intro adapted from Wikipedia (CC BY-SA).
Borax is an IMA-recognized mineral species in the borate class, with the chemical formula Na₂B₄O₅(OH)₄·8H₂O.
It crystallizes in the monoclinic crystal system (space group C2/c).
Key properties: Mohs hardness 2–2.5; specific gravity 1.715; typically colorless or white or gray; White streak; Vitreous to resinous, may be earthy luster; optically biaxial.
IMA symbol Brx, grandfathered status — known before the IMA’s founding.
Found in evaporite deposits, salt lakes, playas, commonly well-crystallized; as an efflorescence on soils in arid regions.
It is found associated with Inyoite, ulexite, colemanite, kernite, kurnakovite, trona, aphthitalite, glauberite, calcite, nitratine, gaylussite, hanksite, halite, gypsum.
The name comes from the Arabic for white.
Collections: Everyday Minerals.