EXPERIMENT IN MINERALOGY. 259 



In a remarkable paper published in the new Zeitschrift 

 fur praktische Geologie he has extended these views to 

 the nickel ores, and has shown that the nickeliferous 

 sulphides in many parts of the world have probably been 

 concentrated in a similar manner (23). At Esteli in Nor- 

 way, Klefva in Sweden, Varallo in Piedmont, and Sudbury 

 in Canada, nickeliferous pyrrhotite associated with copper 

 pyrites, ilmenite, etc., is the ore, and it occurs in gabbro 

 (norite). 



(In connection with what has been said above, it is inter- 

 esting to note that some of the Sudbury nickel ore is platini- 

 ferous, and that an arsenide of platinum has been found 

 in the district (24).) 



The well-known nickel ores of New Caledonia are mostly 

 silicates, and are associated with chalcedony, brucite, mag- 

 nesite and other alteration products, but here also they 

 occur in serpentine, i.e., in an altered basic rock from which 

 again the nickel may have been derived by concentration. 

 Vogt himself, however, does not incline to this opinion. 



These and similar views reoardinQf magmatic concentra- 

 tion, which are rapidly finding acceptance among geologists 

 and petrologists, are referred to here as examples both of 

 the value of experimental evidence and of the need of it. The 

 order in which minerals crystallise from a siliceous magma 

 and the manner in which certain elements unite to form 

 definite minerals have been verified by numerous experi- 

 ments with slags, and it is this that invests Vogt's views 

 upon the concentration of the oxides with a special value. 

 As regards the sulphides and much of the purely pe- 

 nological speculation, the experimental evidence is still 

 wanting. 



On the mineralogical side the subject has considerable 

 practical importance ; for it may lead to a better knowledge 

 of the distribution not only of metalliferous ores but also 

 of the rare elements which, without doubt, do exhibit a 

 tendency to congregate in certain limited areas. 



From every point of view, experimental mineralogy is 

 a subject which has always been strangely neglected in 

 England. 



