296 University of California Publications in Geology [Vol. 13 



While this process was in progress, magmatic juices, probably in small 

 quantity, carried a little aplitic and pegmatitic material into the first 

 fractures formed, and with it, small quantities of ore material. This, 

 however, may be passed by for more significant processes, since these 

 indications of segregation are not inconsistent with what has already 

 been said nor with what is to follow; it is mentioned in this place to 

 give ground for the supposition that in the saturation of the diabase 

 with a fluid medium for the operation of diffusion, the magmatic 

 juices, by largely uniting with the ground water, may be regarded as 

 having made a material contribution. 



When the ground water arrived it may have been saturated with 

 such dissolved substances as lime and magnesium carbonates, silica, 

 alkaline carbonates, and a certain amount of sulphates and sulphides. 

 It must also be supposed that the magmatic juices contributed a cer- 

 tain amount of solvent substances. If it is admitted that sulphurous 

 acid and sulphur may have been present to make thiosulphates with 

 the alkalis, or that the S 2 3 ion may have been produced by such a 

 reaction as : 



S + H 2 = S 2 3 + 3H 2 S, 



then what Roscoe and Schorlemer have to say about thiosulphates 18 



will be of interest : 



Thiosulphates exhibit a great tendency to form double salts; those of the 

 thiosulphates insoluble in water are found to dissolve in an aqueous solution of 

 sodium thiosulphate, which also has the power of dissolving other insoluble salts 

 such as silver chloride, silver bromide, silver iodide, lead iodide, lead sulphate, 

 calcium sulphate, etc., thus: 



^|s 2 0,+ Agd= ^0 3 + Nad 



Na 2 S„0 3 + NiCL + H,0= HJ30 4 + NiS + 2NaCl 

 Na 2 S,0 3 + C'oCL + H„0 = EL S0 4 + CoS + 2NaCl. 



The same authors make reference in another place 19 to the complex 

 nickel silicates, rewdanskite (Ni, Fe, Mg)3Si 2 7 + 2H 2 and garnier- 

 ite, 2(Ni, Mg),Si 4 13 -f 3HoO. It may be useful to bear these in mind 

 in connection with the idea of the impurities assumed for the essential 

 minerals of the diabase. 



The role of arsenic and antimony in these reactions can probably 

 be safely assumed to be in many cases that of partial substitutes for 

 sulphur. At any rate it is to be assumed that the solvent for the 

 ore metals is a solution of sodium thiosulphate, and that the ore ele- 

 ments, being unstable in their false positions in the pyroxenes, etc., 



is Vol. 1, p. 414. is Vol. 2, p. 1040. 



