THE PROBLEM OF THE METALLIFEKOUS VEINS. 



193 



necessary in aliiminiun is in the method of combination. It is so 

 tightly locked np in silicates in the rocks as to preclnde direct extrac- 

 tion by any known method. 



Nickel needs to be present in amounts of several per cent, say 

 2 to 5, and occurs either alone or with copper. Cobalt is always with 

 it in small amounts. Platinum occurs in exceedingly small percent- 

 ages. It is almost all obtained from gravels in Russia, and the 

 gravels yielded in 1899, according to C. W. Purington. about 40 cents 

 to the yard, platinum being quoted in that year at $15 to $18 per 

 ounce. There was therefore in the gravels about one-fortieth ounce 

 in the yard, or one-sixtieth in a ton or about five and a half hundred 

 thousandths of a per cent. Platinum in some rocks has been found 

 in amounts of one-twentieth to one-half ounce, or from sixteen hun- 

 dred thousandths to sixteen ten thousandths of 1 per cent, but they are 

 rare and peculiar types. 



In order to be salable manganese ores of themselves must yield 

 about 50 per cent, l)ut if iron is also present they may be as low as 

 40. Chromium has but one ore, and it must contain about 40 per 

 cent. Of antimony, arsenic, and cobalt, it is hardly possible to speak, 

 since, except perhaps in the case of the first, they are unimportant 

 by-products in the metallurgy of other ores. 



In summary it may be stated that in the ores the metals must 

 be present in the folloAving amounts : 



We now have before us some fundamental conceptions from which 

 as a point of departure we may set out upon the real discussion of 

 the subject. We understand the gross composition of the outer 

 earth ; we have some idea of the quantitative distribution of the metals 

 in the rocks, especially in the richer instances; finally we have seen 

 the extent to which they must be concentrated in order that they may 

 be objects of mining. The next step is to establish, first, the agent 

 or solvent which can effect the collection of the sparsely distributed 



SM 1900^ 13 



