Schiavinatoite
| Schiavinatoite | |
|---|---|
| General | |
| Category | Borate mineral |
| Formula | NbBO4 |
| IMA symbol | Shv |
| Strunz classification | 6.AC.15 |
| Crystal system | Tetragonal |
| Crystal class | Ditetragonal dipyramidal (4/mmm) H-M symbol: (4/m 2/m 2/m) |
| Space group | I41/amd |
| Unit cell | a = 6.22, c = 5.49 [Å] (approximated); Z = 4 |
| Identification | |
| Color | Colorless |
| Crystal habit | zones of prismatic dipyramidal crystals (intergrown with béhierite) |
| Mohs scale hardness | 8 |
| Luster | Vitreous |
| Streak | White |
| Density | 6.55 |
| Optical properties | Uniaxial (+) |
| Refractive index | n=2.30 |
| Birefringence | Yes |
| References | |
Schiavinatoite is a very rare borate mineral, and the niobium endmember of a (Nb,Ta)BO4 solid solution formed with béhierite.
Schiavinatoite is classified as monoborate. It contains tetrahedral borate anion instead of planar BO3 group, which is more common among minerals. Schiavinatoite is one of the most simple niobium minerals. Both minerals possess zircon-type structure (tetragonal, space group I41/amd) and occur in pegmatites. Schiavinatoite and nioboholtite are minerals with essential niobium and boron.