Berborite
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 on natrolite | |
| General | |
| Category | Borate minerals |
| Formula (repeating unit) | Be2(BO3)(OH,F)•H2O |
| Strunz classification | 6.AB.10 |
| Dana classification | 26.1.1.1 |
| 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) |
| Identification | |
| 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 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]
References