Carbonates: Bura
Diagnostic card.
Na 2 B 4 O 5 (OH) 4 * 8 (H 2 O)
Singonia monoclinic
Hardness 2-2,5
Specific gravity 1,7-1,8
Cleavage is perfect
Broken shell (brittle)
Color is colorless, white, gray, yellow
Powder in color from white to gray
Glitter is glass, bold, waxy
Occurs in the form of compact masses, but sometimes come across beautiful, slightly elongated, prismatic crystals, sometimes tabular. They are usually found in a dense mass of borax.
Diagnostic signs.
In air, the borax is converted to tinalkonite (Na2B4O5 (OH) 4 * 3H2O). The latter forms a white opaque film on borax crystals, which eventually completely collapse.
Origin.
It occurs in deposits formed during the evaporation of boron-containing brines of lakes; Is associated with halite and other minerals of evaporites.
Deposits and applications.
Since ancient times, Kashmir and Tibet are known deposits: in small quantities, the drill was mined in Russia and Iran. In Italy, there were reports of finds in Larderello in the Tuscany region. Economically significant deposits were discovered in the United States, primarily in California. There are particularly famous (including the wonderful crystals) Borax Lake, Boron, Furnas Creek and Searls Lake.
Bura. Boron, California, USA. Photo: © А.А. Evseev.
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