i9o6.] SMITH— PARAGENESIS OF MINERALS. 185 



crushed and sheared ahnost everywhere, even where no glauco- 

 phane has been developed in them. Yet, in a sense, the phenomenon 

 is regional, that is, confined to a petrographic region, or, more prop- 

 erly, a region of one sort of geologic activity. 



Neither in the Rocky Mountain, the Lake Superior, nor in the 

 Appalachian region, are glaucophane schists developed; although 

 amphibole and garnet schists are common. Nor yet in the Sierra 

 Nevada of California, where extensive schist masses, both of dy- 

 namic and of contact origin, are common, is any glaucophane schist 

 known. And there, too, extensive masses of peridotites occur, and 

 altered sediments of the same chemical character as in the Coast 

 Ranges, but of totally different petrographic character. Altered 

 quartzites are abundant in the Sierra Nevada, also altered clay 

 shales and altered diabase tuffs. But the quartzites have been 

 changed to sericite schists, the clay shales to andalusite schists, and 

 the diabase tuffs and the peridotites to amphibolites, all without 

 glaucophane. And, what is more puzzling, the metamorphism in the 

 Sierra Nevada and in the Coast Ranges seem to have been con- 

 temporaneous. 



Minerals of the Glaucophane-bearing Rocks. 

 Primary Minerals. 



Under this head are treated those minerals that were present in 

 the original rock, and have remained unaltered. Feldspars were 

 important constituents of the original rocks, both igneous and sedi- 

 mentary, but they have rarely resisted the readjustment consequent 

 upon metamorphism. In a quartz diorite from Oak Ridge, about 

 five miles east of Calaveras Valley, Santa Clara County, the original 

 oligoclase is largely intact, though decomposed in spots where sec- 

 ondary glaucophane (crossite) and lawsonite have been formed. 



The original labradorites of the pseudodiorites and the pseudo- 

 diabases (altered diabases) of Sulphur Bank and other localities 

 are partly preserved as such, although usually they are entirely de- 

 composed. In general, the feldspars have been the first minerals 

 altered, as can be seen in the pseudodiabases, where often the horn- 

 blende or the augite is unaltered, and the feldspars are changed to 

 a saussuritic mass. 



