772 E. C. ANDREWS 



the tin minerals may be seen to be intimately related to the siliceous 

 granites. The molybdenite deposits are almost always within 

 the marginal development of the siliceous granites, while tourmaline, 

 topaz, and allied minerals are characteristically absent. Contact 

 deposits of molybdenite in Australia, as, for instance, at Yetholme 

 (New South Wales), are rare. 



Although these granites in Australia accompanied strong 

 folding movements, and although ore deposits in that continent 

 appear to have been dependent upon strong folding phenomena, 

 nevertheless it must not be inferred that all periods of folding in 

 Australasia have been associated with the formation of ore deposits 

 on a commercial scale, but simply that all ore deposits of com- 

 mercial importance in Australasia are intimately related in some 

 way to periods of folding. This statement refers, naturally, only 

 to deposits of the metallic minerals. 



a) Western Australia : The vast area of Western Australia con- 

 sists, in the main, of highly altered rocks of pre-Cambrian age. 

 These schists and allied types are intruded by siliceous granites 

 and allied rocks, which also are considered to be pre-Cambrian in 

 age. "The old granite rocks are traversed by many large ice-like 



quartz reefs These older granite rocks .... form the 



matrices of the tin and allied deposits of the state." 1 



This mineral has been found to the extent of about 14,000 tons in 

 Western Australia, while wolfram is subordinate in amount. 

 Molybdenite has been recorded in small scattered flakes from this 

 area. 



b) Northern Territory : The rocks of the Northern Territory are 

 extremely old, probably pre-Cambrian in many places. Tin and 

 wolfram to the values respectively of £400,000 and £40,000 approxi- 

 mately have been won from the Northern Territory. Molybdenite 

 has been reported, but it has not been worked as yet. 



c) South Australia: The ore deposits of South Australia 

 are very old. Tin, wolfram, and molybdenite have been found 

 in this state, but the amounts won are too negligible to be 

 considered. 



1 A. Gibb Maitland, "Mining Fields of Australia" (Federal Handbook), Brit. 

 Assoc. Adv. Sci., Australia meeting, 1914, pp. 446-47. 



