Béhierite
General
CategoryBorate
Formula
(repeating unit)		(Ta,Nb)BO4
IMA symbolBéh[1]
Strunz classification6.AC.15
Crystal systemTetragonal
Crystal classDitetragonal dipyramidal (4/mmm)
H-M symbol: (4/m 2/m 2/m)
Space groupI41/amd
Unit cella = 6.21, c = 5.47 [Å] (approximated); Z = 4
Identification
Crystal habitpseudo-octahedral
Cleavage{110} and {010}, distinct
FractureSubconchoidal
Mohs scale hardness7-7.5
Density7.91 (calc.), 7.86 (meas.)
Optical propertiesUniaxial (+)
Refractive indexnω & nε >2
BirefringenceHigh
References[2][3]

Béhierite is a very rare mineral,[2] a natural tantalum borate of the formula (Ta,Nb)BO4.[4][3] 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. It forms a solid solution with its niobium-analogue, schiavinatoite. Both have zircon-type structure (tetragonal, space group I41/amd) and are found in pegmatites.[3] 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.[3]

Occurrence and association

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.[2]

Crystal structure

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]

References

  1. ↑ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. 1 2 3 "Béhierite (Ta,Nb)BO4 - Handbook of Mineralogy" (PDF). Handbookofmineralogy.org. Retrieved 2016-03-03.
  3. 1 2 3 4 "Béhierite: Béhierite mineral information and data". Mindat.org. Retrieved 2016-03-03.
  4. ↑ Mrose, M.E., and Rose, H.J., 1961. Behierite, (Ta,Nb)BO4, a new mineral from Manjaka, Madagascar. Geological Society of America, Abstracts Annual Meetings 1961, 111A-111A
  5. ↑ "Holtite: Holtite mineral information and data". Mindat.org. Retrieved 2016-03-03.
  6. ↑ Range, K.J., Wildenauer, M., and Andratschke, M., 1996. Crystal structure of tantalum orthoborate, TaBO4. Zeitschrift für Kristallographie, 211-215
  7. ↑ Demartin, F., Diella, V., Gramaccioli, C.M., and Pezzotta, F., 2001. Schiavinatoite, (Nb,Ta)BO4, the Nb analogue of behierite. European Journal of Mineralogy 13, 159-165
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