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Formula: CaB2O(OH)6.2H2O
Hydrated borate containing hydroxyl
Crystal System: Triclinic
Specific gravity: 2.00 to 2.03 measured, 2.02 calculated
Hardness: 2½
Streak: White
Colour: Colourless
Environments
Sedimentary environments
Metamorphic environments
Pentahydroborite occurs in skarn (Webmin).
Localities
At the Shijiang Shan-Shalonggou mining area, Inner Mongolia, China, the mineral deposits occur predominantly in
veins of hydrothermal origin in skarn. Pentahydroborite occurs
as clusters of platy to wedge-shaped colourless crystals to 12 mm, freestanding on the walls of cavities. Associated
minerals include andradite, minor
galena and wurtzite, but no other
borate mineral has been observed associated with pentahydroborite
(R&M 96.5.404)
At the type locality, the Novofrolovskoye B-Cu deposit, Tur'insk, Turya river, Turinsk-Auerbakovsk ore field, Serovsky District,
Sverdlovsk Oblast, Russia, pentahydroborite occurs in boron-rich iron ore skarn
as small grains associated with
andradite-grossular,
magnetite, frolovite and
szaibélyite
(AM 47.1482-1485, Mindat, HOM).
At the Pobrdzhsky Potok & Peskanya deposits, Baljevac na Ibru, Jarandol Basin, Raška, Raška District, Central Serbia,
pentahydroborite occurs in in a volcanogenic-sedimentary borate deposit associated with
colemanite, howlite,
ulexite and studenitsite
(HOM).
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