THE MINERALS OF TASMANIA. 79 



variety, chalcotrichite, occurs in small capillary tufts of an 

 intense crimson colour at the Colebrook Mine, near Ring- 

 ville. The sapphire occasionally abounds in tin-drift in the 

 North-East mining districts, and is sometimes of the beauti- 

 ful royal blue so eagerly sought after by gem-hunters. The 

 pleonaste, or black spinel, on the same tin-fielcls, is one of 

 the many common minerals known to the miner as " Black 

 Jack." On the Zeehan and Dundas field very fine speci- 

 mens of stilphnosiderite and massicot have been met with. 

 Cassisterite occurs in fine, well-developed, intensely black 

 crystals — often macled — at the Lottah Mine at Blue Tier, 

 Bell Mount, and Storey's Creek, in the Ben Lomond district. 

 At Constables' Creek, on the North-East Coast, bunches of 

 well-formed mahogany-coloured crystal groups have been 

 met with, and at Mount Bischoff the impregnations of this 

 mineral in the local topaz-porphyry are of special interest. 



At the Rex Hill Mine, the tin-ore is impregnated through- 

 out a granite rock, in which the large orthoclase crystals are 

 pseudornorphed to cassiterite, this being the first recorded 

 instance of such a replacement in this State, or, perhaps, 

 outside the classical locality in Cornwall, England. Alluvial 

 tin is found in great profusion of colouration ; it varies from 

 glassy (almost colourless), to amber, brown, and ruby, hence 

 the local appellatious of resin tin, ruby tin, and so on. 



Among the oxides of the elements of the arsenic and 

 sulphur groups, nothing worthy of special mention has been 

 exhumed, with the exception of wolframite, bismite, and 

 cervantite. 



Chief among the elements of the carbon-silicon group is 

 the oxide of the latter quartz. It appears here in hosts of 

 varieties, even for so variable a mineral. Among the more 

 common forms are rock crystal, chalcedony, cornelian, ca- 

 cholong, and infusorial earth. The milk-opal, with an oc- 

 casional splash of the fire and colour of the precious variety, 

 is abu.ndant, impregnating and seaming the Permo-Carbon- 

 iferous sandstone at Bothwell, and wood opal (silica after 

 organic matter) has been obtained in very beautiful and 

 perfect examples, so much so that much of the material is 

 worthy the attention of the lapidary. In the bi-silicateg, 

 which comprise the rock forming iron-magnesium minerals, 

 are pyroxene and hornblende, with their array of conflicting 

 variations, both as regards diversity of colour and growth. 

 In the Heazlewood district, the rhombic foi'm, bi'onzite, and 

 its variety bastite, are obtained in characteristic develop- 

 ment, and the monoclinic diallage, often altered to schiller- 

 spar, occurs at the same locality. Well-formed crystals of 



