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Category Borate minerals
(repeating unit)
Strunz classification 6.AB.10
Dana classification
Crystal system 1T polytype: Trigonal
2H polytype: Hexagonal
2T polytype: Trigonal
Crystal class 1T polytype: Pyramidal (3)
2H polytype: Pyramidal (6)
2T polytype: Ditrigonal pyramidal (3m)
Unit cell a = 4.43 Å, c = 5.34 Å;
Z = 2; V = 90.76 Å³ (2H polytype)
Color Colorless
Twinning Complex
Cleavage {0001} Perfect
Fracture Uneven - Flat surfaces (not cleavage) fractured in an uneven pattern.
Mohs scale hardness 3
Luster Vitreous (Glassy)
Streak white
Diaphaneity Transparent
Density 2.2
Optical properties Uniaxial (-)
Refractive index nω = 1.580 nε = 1.485
Birefringence δ = 0.095
Ultraviolet fluorescence none
References [1][2][3][4]

Berborite is a beryllium borate mineral with the chemical formula Be2(BO3)(OH,F)·(H2O). It is colorless and leaves a white streak. Its crystals are hexagonal to pyramidal. It is transparent and has vitreous luster. It is not radioactive. Berborite is rated 3 on the Mohs Scale.[2]

Berborite occurs in 1T, 2T, 2H polytypes.[3]

It was first described in 1967 for an occurrence in the Lupikko Mine, Ladoga Region Karelia Republic, Russia. It has also been reported from Tvedalen, Larvik, Vestfold, and Siktesøya Island, Langesundsfjord, Porsgrunn, Telemark, Norway.[1][3] It occurs in serpentine altered dolostone in association with skarn enriched in tungsten, strontium, beryllium and boron in the Keralia occurrence and in vugs with natrolite and thomsonite in Norway.[2][3]