| Béhierite | |
| Category: | Borate |
| Formula: | TaBO4 |
| Imasymbol: | Béh[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 = 6.21, c = 5.47 [Å] (approximated); Z = 4 |
| Habit: | pseudo-octahedral |
| Cleavage: | and, distinct |
| Fracture: | Subconchoidal |
| Mohs: | 7-7.5 |
| Refractive: | nω & nε >2 |
| Opticalprop: | Uniaxial (+) |
| Birefringence: | High |
| Density: | 7.91 (calc.), 7.86 (meas.) |
| References: | [2] |
Béhierite is a very rare borate mineral, and the tantalum endmember of a solid solution series formed with schiavinatoite, its niobium analogue.[3] [4]
Béhierite is also one of the most simple tantalum minerals. It contains simple tetrahedral borate anions, instead of more common among minerals, planar BO3 groups. Both have zircon-type structure (tetragonal, space group I41/amd) and are found in pegmatites. Béhierite and holtite are minerals with essential tantalum and boron.[5]
Béhierite was named for Jean Béhier (1903 - 1965), who discovered the mineral in 1959, as a French mineralogist, active in the Service Géologique, on the island of Madagascar.[4]
Béhierite occurs in granitic pegmatites in Manjaka and Antsongombato, Madagascar. Associated minerals are albite, manganese-bearing apatite-group mineral, lepidolite, elbaite or elbaite–liddicoatite, feldspar, pollucite, quartz, rhodizite, and schiavinatoite.
Crystal structure of synthetic TaBO4 was refined by Range et al. (1996).[6] As béhierite is analogous to schiavinatoite, their crystal structures are expected to be similar.[7]