Borax (mineral)

For commercial sodium borates, see Borax.

Borax
Borax from the Kramer Borate deposit, Boron, Kern Co, California, USA
General
Category	Nesoborate
Formula (repeating unit)	Na2B4O5(OH)4·8H2O
IMA symbol	Brx[1]
Strunz classification	6.DA.10
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	C2/c (no. 15)
Unit cell	a = 11.8790(2) Å, b = 10.6440(2) Å, c = 12.2012(2) Å; β = 106.617(1)°; Z = 4
Identification
Color	Colorless or white
Crystal habit	As prismatic crystals or as massive encrustations
Twinning	Rare on {100}
Cleavage	Perfect on {100}, less perfect on {100}, very poor on {010}
Fracture	Conchoidal
Mohs scale hardness	2 to 2.5
Luster	Vitreous to resinous to earthy
Streak	White
Diaphaneity	Translucent to opaque
Specific gravity	1.715
Optical properties	Biaxial (-)
Refractive index	nα = 1.4466 nβ = 1.4687 nγ = 1.4717
Fusibility	1.5
Diagnostic features	Froths on heating, producing a yellow flame
Solubility	Soluble in water
References	[2][3][4][5]

Borax (Na₂B₄O₅(OH)₄ · 8 H₂O[2]) is a borate mineral found in evaporite deposits of alkaline lacustrine environments and as a surface efflorescence in arid regions. It is the chief mineral mined from the deposits at Boron, California and nearby locations, and is the chief source of commercial borax.[5]

Borax first reached Western civilization as tincal mined from deposits in Tibet.[5] The term borax comes from the Arabic bauraq, meaning white.[3]

Occurrences

The most extensive deposits are in Kirka, Turkey. Borax is also mined in the Andes Mountains of Argentina, Bolivia, and Chile. However, the greatest production is from the deposits in California.[5]

Uses

Natural occurrences of the mineral are an important source of commercial borax, which is used for the manufacture of glass fibers, in cleaning agents, as an antiseptic, and as a flux in metallurgy and solvent for metal oxides.[5]

See also

• List of minerals

References

1. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
2. Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C. (2005). "Borax" (PDF). Handbook of Mineralogy. Retrieved 17 June 2022.
3. "Borax". Mindat.org. Retrieved 17 June 2022.
4. Sinkankas, John (1964). Mineralogy for amateurs. Princeton, N.J.: Van Nostrand. pp. 382–383. ISBN 0442276249.
5. Klein, Cornelis; Hurlbut, Cornelius S. Jr. (1993). Manual of mineralogy: (after James D. Dana) (21st ed.). New York: Wiley. pp. 421–422. ISBN 047157452X.