Molybdenite Composition, Crystallization, Structure and Occurrence

Composition. Molybdenum disulphide, MoS2 = Sulfur 40, molybdenum 60.

Crystallization. Hexagonal. Crystals in hexagonal-shaped plates or short, slightly tapering prisms.

Structure. Commonly foliated massive or in scales.

Physical Properties. Perfect basal cleavage. Lamine flexible but not elastic. Sectile. H. = 1. G. = 4.75. Greasy feel. Metallic luster. Color lead-gray. Grayish black streak.

Test. infusible. Heated B.B. gives yellowish green flame. Roasted in O.T. gives odor of sulfur dioxide and deposit of thin plates of molybdenum oxide, crossing the tube above the mineral. Heated on charcoal in O.F. gives a white coating of molybdenum oxide; when this coating is touched with R.F. turns to deep blue color. When heated with potassium iodide and sulfur on a plaster tablet gives a deep blue sublimate. Resembles graphite but is distinguished form it by having a blue tone to its color, while graphite has a brown thing, and by its reactions for sulfur and molybdenum.

Occurrence. In pneumatolytic contact deposits with cassiterite, scheelite, wolframite, fluorite, etc. Also found in pegmatite and quartz veins associated with granite, gneiss, syenite, etc.; more rarely in limestones. Occurs with the tin ores of Bohemia; from various places in Norway; form New South Wales. Found in the United States in many localities, but usually not in commercial quantity. Found at Blue Hill, Maine; Westmoreland, New Hampshire; in Okanogan County, Washington. From various places in Ontario, Canada.

Use. An ore of molybdenum. See under wulfenite.