Monoclinic, pseudohexagonal. Becomes truly hexagonal at 140°C.
G = 2·8. H = 6. Yellow to brown; transparent to opaque.
A blue variety is known which contains no calcium.
Islands of Langesund Fiord, Norway; Narsarsuk, Greenland.
Cerite.
A basic silicate of Cerium metals, with Ca and Fe. Approximately H₃(Ca,Fe)Ce₃Si₃O₁₃. Cer = 50·7-71·8%. In a variety from Batoum, Tschermak reports Yttr = 7·6 and ZrO₂ = 11·7%.
Orthorhombic; usually massive or granular.
G = 4·9. H = 5-6. Brown to red; translucent to opaque.
Ryddarhyttan, Sweden; Batoum, Caucasus?