What is "zirkelite"

n. (context mineralogy English) An isometric oxide mineral with the chemical formula (Ca,Th,Ce)Zr(Ti,Nb)₂O₇.

Zirkelite is an oxide mineral with formula: ( Ca, Th, Ce) Zr( Ti, Nb) O. It occurs as well-formed fine sized isometric crystals. It is a black, brown or yellow mineral with a hardness of 5.5 and a specific gravity of 4.7.