| Béhierite | |
| Category: | Borate |
| Formula: | (Ta,Nb)BO4 |
| 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 mineral, the tantalum endmember of a borate solid solution series with formula .[3] [4] The niobium analogue is schiavinatoite.
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]