Tags: Chemical Substance, Mineral.
Omphacite is a member of the pyroxene group of silicate minerals with formula: (Ca Na)(Mg Fe2+ Al)Si2O6. It is a variably deep to pale green or nearly colorless variety of pyroxene. Omphacite compositions are intermediate between calcium-rich augite and sodium-rich jadeite. It crystallizes in the monoclinic system with prismatic typically twinned forms though usually anhedral. Its space group (P2/n) is distinct from that of augite and jadeite (C2/c).