MOLYBDENITE  , a

mineral consisting of molybdenum disulphide, MoS2 . It closely resembles graphite in appearance, but may readily be distinguished from this by its greater density (4.7) and by its behaviour before the blowpipe . Crystals have the form of six-sided plates or scales, but they are never sharply defined, and their reference to the hexagonal system is doubtful . They have a perfect cleavage parallel to the large surface of the plates, and the flakes are readily bent, but are not elastic . The mineral is very soft (H = 1 to I z) and unctuous, and makes a bluish-grey mark on paper: it is opaque and has a bright metallic lustre . The colour is lead-grey differing slightly from that of graphite in having a bluish tinge . The name molybdenite is from the Greek /2c Xu(3Sos, meaning lead or lead ore, with which graphite (black-lead) and molybdenite were confused; the latter was distinguished by P . J . Hjelm, who in 1782 discovered the element molybdenum in this mineral . Molybdenite occurs as disseminated scales in crystalline rocks—such as granite, gneiss, schist and marble—and also in quartz-veins . It has been found in small amounts at many localities, but only those which have yielded large crystals need be specially mentioned here, viz. in a pyroxene-rock at Aldfield in Pontiac county, Quebec; with native bismuth at Kingsgate in Gough county, New , South Wales; with wolframite and scheelite in quartz-veins at Caldbeck Fells in Cumberland; and recently, as crystals 6 in. across, at Slangsvold near Raade in Norway . Molybdenite has been used mainly for the preparation of molybdates for use as chemical reagents .

Recently, however, it has been used in the manufacture of molybdenum

steel (ferro-molybdenum), which by reason of its hardness and toughness is specially suitable for tools . (L . J .