polyhalite

[Pref. poly-, and Eng. halite.] Min.: A mineral occurring mostly in closely compacted fibrous ma es. Crystallization, according to some mineralogists, orthorhombic, to others, oblique. Hardne , 2.5-3; specific gravity, 276, luster, when fresh, somewhat resinous; color and streak, pale to brick-red; taste, bitter. Composition: Sulphate of lime, 45'2; sulphate of magnesia, 19-9; sulphate of potash, 28.9; water, 6.0=100, corresponding to the formula, RO, SO3+HO, in which R=potash, magnesia, and lime. Found a ociated with salt, gypsum, and anhydrite at many salt mines. pol-ý-he-dral, põl-y-he-droŭs, adj. [POLYHEDRON.] Having many sides, as a solid body. polyhedral-angle, subst. An angle bounded by three or more plane angles, having a common vertex.