Béhierite

Béhierite
Béhierite
General
Category	Borate
Formula; (repeating unit)	(Ta,Nb)BO4
IMA symbol	Béh[1]
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	[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

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.
"Béhierite (Ta,Nb)BO₄ - Handbook of Mineralogy" (PDF). Handbookofmineralogy.org. Retrieved 2016-03-03.
"Béhierite: Béhierite mineral information and data". Mindat.org. Retrieved 2016-03-03.
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
"Holtite: Holtite mineral information and data". Mindat.org. Retrieved 2016-03-03.
Range, K.J., Wildenauer, M., and Andratschke, M., 1996. Crystal structure of tantalum orthoborate, TaBO₄. Zeitschrift für Kristallographie, 211-215
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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[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.

[H-2] "Béhierite (Ta,Nb)BO₄ - Handbook of Mineralogy" (PDF). Handbookofmineralogy.org. Retrieved 2016-03-03.

[Min-3] "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