Borate mineral

Large (up to 1.8 cm) yellow londonite crystals associated with rubellite tourmaline. Londonite is an unusual caesium-rich heptaborate.^[1]

The Borate Minerals are minerals which contain a borate anion group. The borate (BO₃) units may be polymerised similar to the SiO₄ unit of the silicate mineral class. This results in B₂O₅, B₃O₆, B₂O₄ anions as well as more complex structures which include hydroxide or halogen anions.^[2] The [B(O,OH)₄]⁻ anion exists as well.

Many borate minerals, such as borax, colemanite, and ulexite, are salts: soft, readily soluble, and found in evaporite contexts. However, some, such as boracite, are hard and resistant to weathering, more similar to the silicates.

There are over 100 different borate minerals.^[2]^[3] Borate minerals include:

Kernite Na₂B₄O₆(OH)₂·3H₂O
Borax Na₂B₄O₅(OH)₄·8H₂O
Ulexite NaCaB₅O₆(OH)₆·5H₂O
Colemanite CaB₃O₄(OH)₃·H₂O
Boracite Mg₃B₇O₁₃Cl
Painite CaZrAl₉O₁₅(BO₃)

^ Londonite at Mindat.org
^ ^a ^b Klein, Cornelis and Cornelius Hurlbut, Jr., Manual of Mineralogy, Wiley, 20th ed., 1985 pp. 343 - 347 ISBN 0-471-80580-7
^ Webmineral.Com, Strunz group V/G - V/L

[1] Londonite at Mindat.org

[Klein-2] Klein, Cornelis and Cornelius Hurlbut, Jr., Manual of Mineralogy, Wiley, 20th ed., 1985 pp. 343 - 347 ISBN 0-471-80580-7

[3] Webmineral.Com, Strunz group V/G - V/L

[1]

[2]

[3]