BY LEO A. COTTON. 751 



preferential concentration of metallic contents near contacts, is a 

 feature which has been observed in many other parts of the 

 world. Of the occurrence at Vegetable Creek, Professor David"*^ 

 has written : " On consulting the geological map accompanying 

 this report it will be noticed that the commencement of most of 

 the veins is situated near the junction of the cla3^stone with the 

 intrusive granite, so that the upward limit of the veins may be 

 said to be the bottom of the claystone and top of the granite. 

 The man ^^^^ shows that, as a rule, the granite at a distance of 

 over IJ mile from its junction with the claj'stone ceases to be 

 tin-bearing." 



In commenting on this statement witli regard to its application 

 to the Stanthorpe area in Queensland, Mr. Skertchlyf says ; 

 *' The tin-bearing beds are here shown to be tlie slates near the 

 granite junction, and just those parts of the granite which were 

 assuredly once covered with slate, and, moreover, by far the 

 larger area of the granite where it is coarsely crystalline and 

 must have solidified at great depth under great pressure, is 

 barren of tin. The acknowledged richness of the country on 

 either side of the junction of the granite and slate must he 

 admitted, and it is no argument against this view that in 

 the Stanthorpe area the richest deposits are often many miles 

 fiouj the boundary, unless it can be shown that the slates never 

 existed there." 



Mr. E. C. Andrews J dealing with the New England tin-ore 

 d^'posits remarks with regard to them that " The ores in almost 

 every important example are arranged peripherally with respect 

 to the acid granite massifs." 



Again with respect to the ore-distribution of Cornwall, Reid 

 and Flett§ have stated: "Tin and copper mining in Cornwall 



* Loc. cit. 



t Skertchly, S. B. J., "On the Geology of the Country round Stanthorpe 

 and Warwick, South Queensland, with especial Reference to the Tin and 

 Gold Fields and the Silver Deposits." Published by Queensland Geological 

 Survey. 1898. 



X Loc. cit. 



§ Reid, C, and Flett, J. S., " The Geology of the Land's End District." 

 Memoir Geol. Surv. England and Wales, 1907. 



