92 THE MINERALS OF TASMANIA. 



have originated by the substitution of iron, which 

 has in other words been replaced by metasomatic 

 action. Pseudomorphs of various minerals to this ore are 

 not by any means rare, and organisms such as certain 

 mollusca and corals are occasionally so altered. Such 

 examples offer emphatic evidence in favour of the replace- 

 ment theory, which may have been carried on in favour- 

 able rock-masses^ which were likewise suitably located. 

 On the other hand, ferruginous matter may, under certain 

 conditions, by precipitation and percolation have occupied 

 vughs or cavities in the rocks, and after consolidation 

 may have been exposed by denudation. It has been stated 

 that the intrusion of acid rocks, such as the granites, 

 has been a primary factor in many occurrences, and there 

 is evidence to show that this assumption is not without 

 reason. At the Blythe Eiver an enormous mass, which 

 boldly outcrops on the banks of the stream, is well known. 

 It has been estimated to contain many millions of tons, a 

 calculation which is confirmed by the prospecting opera- 

 tions which have been carried out. It is a hard massive 

 ore of a bluish purple colour, which gives the normal 

 reddish-brown powder. Throughout small cavities occur, 

 which are occasionally lined with minute crystals. It is 

 reported to be well adapted for the manufacture of pig- 

 iron, and to be remarkably free from deleterious sub- 

 stances. 



An average sample over the whole deposit gives the fol- 

 lowing complete analysis: — 



Ferric oxide 86-954 / «„ ^_„ ^ . 



Ferrous oxide 3.(^74 J 63-259 per cent, iron 



Silica 7-312 per c^nt. 



Alumina 1-756 „ 



Lime .. 0-068 „ 



Magnesia 0-071 „ 



Sulphur trioxide 0-060 per cent., 0-024 per cent. 



sulphur 



Phosphorus pentoxide... 0-083 per cent., 0-036 per cent. 



phosphorus 



Titanic acid . ... 0-03 per cent. 



Copper Trace 



Arsenic Trace 



Manganese Trace 



Chromium Absent 



Combined w:^ter 0*324 per cent. 



Moisture 0-160 



99 • 892 



(" Report from the Royal Commission on " The Bonuses 

 for Manufactures Bill," The Parliament of the Common- 

 wealth of Australia, 1904.) 



