192 THE MINERALS OF TASMANIA. 



green shades. Occasionally it is bright-green It has a 

 waxy to resin-like lustre, with a smooth and unctuous feel, 

 with much the general appearance of ordinary steatite. It 

 is always opaque, but shows slight translucency at the edges. 

 There are numerous irregular cleavages, the surfaces of 

 which are usually extremely smooth and polished. All 

 indications of crystalline structure are perfectly masked. 

 The hardness is much lowered = 2 — 2'5. The substance 

 does not respond to the emanations of radium bromide. 

 This may be classed as a member of that most unsatis- 

 factory group known as the hydro-micas, but distinguished 

 by the high sodium contents, as shown by the analysis so 

 kindly undertaken by Mr. Robert Sticht. It apparently 

 occurred in quantity in following the lode at the 

 Shepherd and Murphy Mine associated with considerable 

 fluorite, and not rarely with embedded cassiterite, wolfram- 

 ite, and normal, well-developed, small crystals of topaz, 

 which were in no respect altered. 



The following are the analysis and remarks afforded by 

 Mr. Sticht, viz. : — 



" The analysis of this presented no such difficulties as 

 No. 1, and is as follows: — 



Per cent. 



40*6 (nearly all insoluble) 



37-0 



0-72 



2-29 



6-32 



5-1 



8-4 



100-43 



This mialysis also shows the presence < f liuorite, hs well 

 as a fairly heavy amount of volatile matter, together 

 with which, however, may likewise be included HO, F, &c. 

 There was about 73 per cent, of insoluble residue, which 

 included nearly all of the silica and most of the alumina. 

 It only contained a trace of F, so that the dissociation 

 of the original topazisation was complete ; but very little 

 of the silica went into the portion soluble in acids, 8 per 

 cent, of the alumina accompanying it, together with some 

 of the other elements." 



Although topaz is presumed to originate in the acid 

 rocks, such as granite, by pneumatolytic action, and in 

 some cases to be of secondary origin, it may itself suffer 



