| Schiavinatoite | |
| Category: | Borate, Oxide |
| Imasymbol: | Shv[1] |
| Strunz: | 6.AC.15 |
| System: | Tetragonal |
| Class: | Ditetragonal dipyramidal (4/mmm) H-M symbol: (4/m 2/m 2/m) |
| Symmetry: | I41/amd |
| Unit Cell: | a = 6.22, c = 5.49 [Å] (approximated); Z = 4 |
| Color: | Colorless |
| Habit: | zones of prismatic dipyramidal crystals (intergrown with béhierite) |
| Mohs: | 8 |
| Luster: | Vitreous |
| Refractive: | n=2.30 |
| Opticalprop: | Uniaxial (+) |
| Birefringence: | Yes |
| Streak: | White |
| Density: | 6.55 |
| References: | [2] |
Schiavinatoite is a very rare mineral,[3] the niobium endmember of a borate solid solution with the chemical formula . The tantalum analogue is béhierite. [4] 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.[5]
Schiavinatoite was detected in miaroles of a pegmatite at Antsongombato, Madagascar. It coexists with an apatite-group mineral, béhierite, danburite, elbaite–liddicoatite, feldspar, pollucite, quartz, rhodizite, and spodumene.[2]
The main facts about schiavinatoite's structure:[4]