PLATE XXIII. 



Fia. A. 



(Sp. No. 22953. Without analyzer, x 38.) 



Ehyolite-porphyry rendered schistose by crushiug. Graiiulatiou of the feldspars and the result- 

 ing production of schistose aggregates of secondary quartz, feldspar, and sericite is here shown. 

 The two large areas shown near the center of the tigure were formerly occupied entirely by feldspar. 

 The greater portion of this has now become altered, mere remnants of the original renuiining. This 

 secondary aggregate has especially well-developed parallelism. (Described, p. 93.) 



Fig. B. 



(Sp. No. 32726. With analyzer, x 18.) 



Photomicrograph of aporhyolite-porphyry breccia showing the fractured character of the 

 quartz and feldspar. Certain portions of the section show the perlitic parting, with accumulations 

 in these areas of chlorite. (Described, p. 93.) 



276 



