Anhydrous borate with halogen, forms a series with hydroxylborite
Colour: Colourless, violet or white; colourless in transmitted light
Fluoborite is a rare hydrothermal mineral in skarn developed in metamorphosed
boron-rich magnesian rocks
(Webmin, HOM, Dana).
At the type locality, Tallgruvan, Kallmora, Norberg, Västmanland County, Sweden, fluoborite occurs in a contact metasomatic magnetite deposit (Mindat), associated with magnetite, ludwigite, chondrodite, calcite and possibly szaibélyite (Mindat, HOM, AM 12.266).
At Palabora, Limpopo Province, South Africa, fluoborite occurs sparsely as tufts of fibrous crystals to 10 mm in length, in association with magnetite, iowaite and calcite (R&M 92.5.438).
In the thermally metamorphosed impure limestone at Crestmore, California, USA, fluoborite has been found in dolomitic marble (AM 48.678-683).
At Sterling Hill, New Jersey, USA, some fluoborite has been found as veinlets in an especially pure zincite. In a few instances the veins are fluorite (AM 14.169-172). Associated minerals include mooreite, willemite, fluorite, hydrozincite, pyrochroite, zincite and rhodochrosite (HOM).
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