rSEUDOMOKPHIC SERPENTINE. 125 



of chlorite as probable.' Mica and garnet have been observed elswhere 

 undergoing conversion to serpentine. The mica foils are so small and pos- 

 .sess such irregular outlines in most of the rocks of the Coast Eanges where 

 serpentinization can be traced tliat this change, though probable, cannot 

 be definitely asserted. Garnet is seen in the few slides which show it in 

 process of conversion to chlorite; but a change to serpentine has not been 

 distinctly traced in the Coast Ranges. Zoisite, as it occurs in these rocks, 

 is not well suited to exhibit pseudomorphic alteration. It appears in smaller 

 quantity in the rocks containing much terpentine, however, than iu those 

 containing little. The prevalence of this mineral in the saussuritic gabbros 

 of Europe, the intimate relations between these rocks and the serpentines, 

 and the absence of observations on the presence of zoisite in massive ser- 

 pentines, either in the Coast Ranges or elsewhere, point towards the prob- 

 ability of a serpentinization. Olivine has not once been detected in the 

 rocks associated with serpentine in the Coast Ranges or iu the serpentines 

 themselves, and olivine cannot have contributed in an appreciable degree to 

 the formation of these serpentines, important as is the part which this min- 

 eral plays in some other serpentinoid areas. 



The chemical changes indicated by the observations described above 

 on the alteration of bisilicates, feldspar, quartz, and apatite to serpentine 

 are very strange, and the results may possibly fail to be accepted by some 

 because of their strangeness. It is a truism, however, that observation 

 almost always outstrips scientific theories, or that these are commonly 

 framed to embrace* the results of observation, while the changes indicated 

 here are not more perplexing than many other reactions once were, for 

 which reasonable explanations have been discovered. Mineral cliemistry is 

 full of puzzles, some of them so familiar that their chemical difficulties are 

 hardlv appreciated. That a number of difterent minerals should all be re- 

 placed by serpentine under certain appropriate conditions is in itself not 

 more remarkable than that from a single solution an equal number of min- 

 erals should be precipitated almost or quite simultaneou.sly; yet in the 

 study of veins such cases occur so frequently that they attract no attention. 



' Lchrbuch cliem. iind phys. Geol., vol. 2, 1864, p. 7S'J. 



