Hauyne

Hauyne, a rock-forming mineral, having approximately the same composition as Nosean. The two are probably only varieties of one and the same mineral. They are anhydrous silicates of alumina and soda, or alumina and lime, with sodium and calcium sulphate. They crystallise in isometric forms, and have a hardness = 5·5·5, and a specific gravity = 2·2–2·5. Hauyne is usually bright blue to bluish-green, while Nosean is generally gray, but sometimes greenish or even dark brown. They are essentially of volcanic origin, occurring as constituents of many recent lavas.