1922] Whitman: Genesis of the Ores of the Cobalt District 293 



As soon as shallower depths are reached by erosion, such that hydra- 

 tion becomes stable, then chlorite, amphibole, serpentine, etc., are 

 formed as a consequence of the presence of the intermolecular water. 

 Or if the rock finds itself in an oxidizing environment before such 

 change can occur, oxygen may diffuse into the crystal substances 

 through the water which lias always been in them, perhaps accom- 

 panied by carbon dioxide, and thus produce alterations more intense 

 along the mineral cleavages and diminishing away from them. With 

 this idea, the fact of fluid inclusions in igneous minerals is in no way 

 incompatible, since such a phenomenon would be 1 interpreted merely 

 as a case where the fluid was in excess of the capacity of the inter- 

 molecular space of the minerals to accommodate it, thus compelling 

 its segregation. 



Water, should it exist in those situations, could not leave them. It 

 would be imprisoned there. Such water as might exist in cleavages 

 and fractures of minerals, as well as water in the rock fractures, must 

 be supposed to be a residuum of segregated magmatic water, or, more 

 probably, meteoric water which has found its way thither by the 

 influence of gravity or capillarity, which forces, according to Van Hise, 

 Posepny, Lawson, Lindgren, Kemp, and others, are adequate to accom- 

 plish that result within the zone of fracture, and perhaps even deeper. 



If diffusion is a considerable factor in geo-chemical processes, it 

 must have many phenomena standing to its credit ; but the existence 

 of a phenomenon is one thing, and the recognition of it another. The 

 mere mention of certain of those phenomena, however, will probably 

 suffice for their acceptance without the necessity of argument. In 

 this category I propose such phenomena as the (1) occurrence of 

 amygdules in vesicular lavas, (2) pseudomorphism, in which case the 

 moleclues of one substance find their way into the interior of another, 

 after replacing its outer portions, and the molecules of the original 

 mineral find their way out, the passage of both being through the pore 

 spaces, or rather, through the intermolecular space of a solid mineral 

 substance, (3) the uniform salinity of the ocean, 17 (4) the remarkably 

 uniform composition of magmas, and particularly the uniform dis- 

 tribution in them, of silica, iron, alumina, lime, magnesia, and the 

 alkalis. In this last case, in spite of the infinite variations of compo- 

 sition of even such fundamental magmas as basalt, their general uni- 

 formity is probably more remarkable than their minor variations. 



" This matter is ably discussed by R. E. Liesegang in his excellent book 

 referred to above. He also discusses a number of other phenomena, important 

 among which is the banding of agates. 



