Pyrochlore

Name:
Pyrochlore
Detailed information:

M Formula:	NaCaNb2O6F
Properties:
A complex oxide of sodium, calcium, and niobium. Tantalum, rare-earth metals, and other elements may be present. Color brown to black, light brown streak. Hardness 5–5.5, d 4.2–6.4.
Occurrence:
Canada (Quebec), Brazil, Africa.
Use:
Ore of niobium.