Zirkelite is an oxide mineral with formula: (Ca,Th,Ce)Zr(Ti,Nb)2O7. It occurs as well-formed fine sized isometric crystals. It is a black mineral with a hardness of 5.5 and a specific gravity of 4.7.
Zirkelite was first discovered in Brazil in 1895. It was named for Ferdinand Zirkel (1838-1912), German petrographer.
Initial discovery was from the Jacupiranga carbonatite, Sao Paulo, Brazil. It is also found in Canada, Kazakhstan, Norway, Russia, South Africa, the United Kingdom, and the USA.