Béhierite
| Béhierite | |
|---|---|
| General | |
| Category | Borate |
| Formula | TaBO4 |
| IMA symbol | Béh |
| 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 = 6.21, c = 5.47 [Å] (approximated); Z = 4 |
| Identification | |
| Crystal habit | pseudo-octahedral |
| Cleavage | {110} and {010}, distinct |
| Fracture | Subconchoidal |
| Mohs scale hardness | 7-7.5 |
| Density | 7.91 (calc.), 7.86 (meas.) |
| Optical properties | Uniaxial (+) |
| Refractive index | nω & nε >2 |
| Birefringence | High |
| References | |
Béhierite is a very rare borate mineral, and the tantalum endmember of a (Nb,Ta)BO4 solid solution series formed with schiavinatoite, its niobium analogue.
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.
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.