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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
Berborite & Natrolite.jpg
Berborite on natrolite
General
CategoryBorate minerals
Formula
(repeating unit)
Be2(BO3)(OH,F)•H2O
Strunz classification6.AB.10
Dana classification26.1.1.1
Crystal system1T polytype: Trigonal
2H polytype: Hexagonal
2T polytype: Trigonal
Crystal class1T polytype: Pyramidal (3)
2H polytype: Pyramidal (6)
2T polytype: Ditrigonal pyramidal (3m)
Unit cella = 4.43 Å, c = 5.34 Å;
Z = 2; V = 90.76 Å3 (2H polytype)
Identification
ColorColorless
TwinningComplex
Cleavage{0001} Perfect
FractureUneven - Flat surfaces (not cleavage) fractured in an uneven pattern.
Mohs scale hardness3
LusterVitreous (Glassy)
Streakwhite
DiaphaneityTransparent
Density2.2
Optical propertiesUniaxial (-)
Refractive indexnω = 1.580 nε = 1.485
Birefringenceδ = 0.095
Ultraviolet fluorescencenone
References[1][2][3][4]

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 dolomite 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]

ReferencesEdit