Bismutotantalite Value, Price, and Jewelry Information
Extremely rare as a cut gem, even in very complete collections. Many of the minerals in the tantalite group have been faceted; bismutotantalite is perhaps the rarest of them all. The color is attractive, but low hardness and good cleavage make use in jewelry unadvisable.
STREAK: Yellow-brown to black
OPTICS: α = 2.388; β = 2.403; γ = 2.428
Biaxial (+), 2V = 80°
OCCURRENCE: Pegmatites.
Gamba Hill, Uganda; Acari, Brazil.
COMMENTS: Extremely rare as a cut gem, even in very complete collections. Many of the minerals in the tantalite group have been faceted; bismutotantalite is perhaps the rarest of them all. The color is attractive, but low hardness and good cleavage make use in jewelry unadvisable.
NAME: On account of the composition.
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