Béhierite

behierite

Images

Formula: Ta(BO4)
Monoborate of tantalum
Crystal system: Tetragonal
Specific gravity: 7.86 measured, 7.91 calculated
Hardness: 7 to 7½
Streak: White
Colour: Greyish pink, pale lilac, colourless to white
Solubility: Insoluble in hot or cold acids
Environments

Pegmatites

Béhierite is a very rare mineral, occurring in granite pegmatites (HOM).

Localities

At the type locality, Manjaka, Sahatany Valley, Ibity, Antsirabe II District, Vakinankaratra, Madagascar, four greyish-pink pseudo-octahedral crystals of béhierite, 0.5 to 7.0 mm in size, were found in a complex lithium - cesium - tantalum granite pegmatite hosted in marble. Associated minerals include albite, manganese-bearing fluorapatite, pollucite, polylithionite-trilithionite series minerals, quartz and tourmaline (Mindat).
Béhierite from Manjaka - Image

At the Antsongombato gem mine, Antsentsindrano, Anosiarivo Manapa, Betafo District, Vakinankaratra, Madagascar, béhierite is associated with schiavinatoite, rhodizite, elbaiteliddicoatite, quartz and feldspar (HOM)
Béhierite from the Antsongombato Gem Mine - Image

At the Animikie Red Ace pegmatite, Pine River pegmatites, Fern, Florence County, Wisconsin, USA, small, transparent, colourless to white crystal grains of béhierite up to 400 microns in size have been discovered in the wall zone of the pegmatite, associated with abundant pink to red elbaite, albite, tantalite-(Mn), quartz and blue manganapatite.
The presence of béhierite in the wall zone of the pegmatite testifies to the very high boron activity that was present at the time of crystallisation and that is essential for the formation of this exotic mineral (R&M 77.170).

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