About Bastnasite

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• Mineralogy and geology*
• Common Associations

Mineralogy and Geology of Bastnasite

Mineral formula: (Ce/Nd/Y/REE)(CO₃)F

Crystal system: hexagonal

Crystal habit: prismatic to fine-grained

Cleavage: Poor on {1010}

Fracture: irregular, uneven

Color: yellow to reddish brown

Luster: vitrous, greasy, or pearly

Diaphaneity: transparent to translucent

Moh’s scale hardness: 4 – 4½

Streak: light blue

Specific gravity: 4.9-5.2

Named after: For the type locality at the Bastnäs mines, Riddarhyttan, Skinnskatteberg, Västmanland, Sweden

Type locality: the Bastnäs mines, Riddarhyttan, Skinnskatteberg, Västmanland, Sweden

Geologic occurrence: This is the most abundant REE mineral, occurring in hydrothermal and primary igneous rocks such as granitic and alkali syenites and pegmatites, carbonatites, contact metamorphic deposits. It occurs rarely in detrital deposits. Often associated with allanite, cerite, tysonite, fluorite, and tornebohmite.

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* Mineralogical information is from mindat.org