Berborite

(repeating unit)Be₂(BO₃)(OH,F)•H₂OIMA symbolBbo^[1]Strunz classification6.AB.10Dana classification26.1.1.1Crystal system1T polytype: Trigonal
2H polytype: Hexagonal
2T polytype: TrigonalCrystal class1T polytype: Pyramidal (3)
2H polytype: Pyramidal (6)
2T polytype: Ditrigonal pyramidal (3m)Space group1T polytype: P3 (no. 143)
2H polytype: P6₃ (no. 173)
2T polytype: P3c1 (no. 158)Unit cella = 4.43 Å, c = 5.34 Å;
Z = 2; V = 90.76 Å³ (2H polytype)IdentificationColorColorlessTwinningComplexCleavage{0001} PerfectFractureUneven - Flat surfaces (not cleavage) fractured in an uneven pattern.Mohs scale hardness3LusterVitreous (Glassy)StreakwhiteDiaphaneityTransparentDensity2.2Optical propertiesUniaxial (-)Refractive indexnω = 1.580 nε = 1.485Birefringenceδ = 0.095Ultraviolet fluorescencenoneReferences^[2][3][4][5]

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.^[3]

Berborite occurs in 1T, 2T, 2H polytypes.^[4]

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.^[2][4] It occurs in serpentine altered dolomite in association with skarn enriched in tungsten, strontium, beryllium and boron in the Karelia occurrence and in vugs with natrolite and thomsonite in Norway.^[3][4]

References