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Metasilicate of Na, Ca, Fe´´, Zr; approximately 4Na₂O,3CaO,14FeO,(Al,Fe)₂O₃,21SiO₂. ZrO₂ = 1-6%.

Monoclinic—an amphibole.

G = 3·44. H = 6. Black; pleochroism strong.

S. Greenland and S. Norway.