Millerite. Capillary Pyrites Composition, Crystallization and Structure

Composition. Nickel sulphide, NiS =sulfur 35.3, nickel 64.7.

Crystallization. Hexagonal- rhombohedral.

Structure. Usually in hairlike tufts and radianting groups of slender to capillary crystals. Sometimes in velvety incrustation.

Physical properties. Cleavage rhombohedral. H. = 3-3.5. G. = 5.65. Metallic luster. Pale brass-yellow; with a greenish tinge when in fine hairlike masses. Streak black, somewhat greenish.

Tests. Fusible at 1.5-2 to magnetic globules. Gives odor of sulfur dioxide when heated on charcoal or in O. T. the roasted mineral colors the borax bead reddish brown in O. F.

Occurrence. Occurs in various localities in Saxony Westplalia and Nassau and in Bohemia; with hematic and siderite at Antwerp, N. Y.; in calcite at St. Louis, Missouri, Keokuk, Lowa, etc.

Use. A subordinate ore of nickel.