120 THE MINERALS OF TASMANIA. 



213. Molybdenite (Disuhphich of Mohjhdenum ). 



This subsitance is found as very characteristic graphite- 

 like flakes, with a high metallic lustre, which are readily 

 severable. The crystals are often met with ; they are 

 hexagonal in form, tabular, and slightly tapering, and are 

 usually implanted in fissures and cavities of the granite 

 or other acid rock to which the species is peculiar. 

 Although found disseminated throughout granites and 

 porphyries, it is more abundant in quartz veins traversing 

 these rocks, and also in pegmatite dykes and pipes. Small 

 crystals fairly well formed are often found at Cape Barren 

 Island, at the Blue Tier, and at the Shepherd and Murphy 

 Mine, Middlesex, but nothing approaching such marvellous 

 crystals and plates of this mineral have been discovered 

 in this island as have been obtained at the Kingsgate 

 mines near Glen Innes, N.S. Wales. No discovery has been 

 made of any commercial importance, although the mineral 

 is widely distributed in the North-E astern and Western 

 tinfields. Occasionally the mineral is obtained coated 

 with a thin layer of molybdic ochre, an oxide resulting 

 from the alteration of the original sulphide, and examples 

 in the matrix from near Lottali show a decomposition to a 

 distinct blue-black substance, which is very likely identical 

 with ilsemannite, which is said to be a molybdate of molyb- 

 dic acid. In the granite and porphyry of the Blue Tier 

 molybdenite is not uncommon, as small flakes and patches 

 in association with cassiterite. It occurs at Heemskirk ; 

 with magnetite and amphibole at a locality 6 miles east 

 of Hampshire, and west of the Blythe River ; at South 

 Flinders and Cape Barren Islands with tin ore ; in garnet 

 rock. Upper Emu River; in tough siliceous rock with 

 columnar hornblende at Highwood on the Upper Blythe 

 River ; with garnet and hornblende in small flakes at the 

 Whyte River ; at Schouten Island ; and many other local- 

 ities of minor importance. The most important use for 

 molybdenum is in the manufacture of molybdenum steel, 

 to which it gives hardness, toughness, and elongation, 

 without any deteriorating effect when heated and welded. 

 It has minor uses in analysis as a reagent, as a disinfect- 

 ant, and in pottery glazes. 



214. MoLYBDiTE (Molyhdic Acid or Oxide). 



Obtained in small quantity as a pulverulent incrustation 

 of a clear yellow colour and dull earthy appearance on a 

 hard dark-coloured siliceous base at the Hampshire Silver 

 Mine (W. R. Bell) ; on lode-matter, mainly greisen and 



