64 TASMANIAN MINERALS. 



in the gossan, where it forms coatings of almost 

 microscopic plates and crystals, which often nestle in 

 little bunches. The crystals are bright and sparkling, 

 usually a shade of yellow to orange, but sometimes 

 a bright crimson. It commonly decomposes to a 

 yellow lead oxide. In the abandoned workings of 

 the old Whyte River Silver Mine, Mr. R. F. Waller 

 obtained some nice slabs of a decomposed rock, liter- 

 ally coated with the characteristic crystals of this sub- 

 stance. Its bright colour renders it an attractive 

 object, but the soft base upon which the crystals are 

 usually implanted causes it to be extremely difficult 

 of transport. It has not so far been noticed at any 

 other of our silver-lead mining locaHties. In fact, 

 its occurrence in the Heazlewood district appears to 

 be the first outside its original locality at Berezov, in 

 the Ural. 



7 Cassiterite {Dioxide of tin.) 



Occurs of unusual habit at Mayne's Mine, Heemskirk. 

 The colour varies from a pale dull grey to almost 

 blacky and is commonly of a radiated fibrous structure 

 in botryoidal and reniform shapes. Where the con- 

 centric structure is well defined, the internal colora- 

 tion is in bands of regular width, of various shades 

 of grey to brown. In all essential characteristics 

 this occurrence exactly corresponds with what is 

 known as " wood tin" in Cornwall, England. 



An acnte pyramidal, intensely black variety, repre- 

 senting what has been termed sparable or " needle" 

 tin in the European mining districts, occurs at 

 Welsh's tin find near the five-mile on the Waratah- 

 Corinna-road. The crystals are minute, very pointed, 

 and a good imitation of the old-world form. 



A remarkable occurrence of cassiterite has recently 

 been discovered at Mount Bischoff by Mr. Bradford, 

 in which cellular cavities, retaining in most insltances 

 the form of orthoclastic felspar, have been lined, and 

 sometimes completely filled, with a mass of minute, 

 welJ-developed, tetragonal tin crystals, combined with 

 pycnite. The cavities are small, but perfectly dis- 

 tinct. The original porphyry has been almost com- 

 pletely topazised, simply leaving gi-anu^ar inter- 

 spersed quartz. The replacement of the felspar with 

 cassiterite is not so complete as that recorded from 

 the Mount Rex Mine, where pseudomorphism has 

 gone to the fullest extent. 



