Scapolite

The scapolites (Gr. asairos, rod, stone) are a group of rock-forming silicate minerals composed of aluminium, calcium, and sodium silicate with chlorine, carbonate and sulfate. The two endmembers are meionite (Ca₄Al₆Si₆O₂₄CO₃) and marialite (Na₄Al₃Si₉O₂₄Cl). Silvialite (Ca,Na)₄Al₆Si₆O₂₄(SO₄,CO₃) is also a recognized member of the group.