HYDRON SILICATES IN ROCKS OF CONCEPTION BAY 133 



spherulites. This structure is characteristic of the white rhyolites 

 of this area and may owe its origin to primary flowage phenomena, 

 or to secondary dynamic forces, or probably to the former 

 accentuated by .the latter. 



DESCRIPTION OF PYROPHYLLITE 



The pyrophyllite veins are of such an extent that they attracted 

 attention as a source of talc; many prospects were opened in the 



Fig. 2. — Lenticular structure in rhyolite. The material surrounding the more 

 massive portions is partially pyrophyllitized . 



deposits and a 2|-mile aerial tram was built to the nearest mine. 

 But, owing probably to the difficulty in separating the pyrophyllite 

 from the admixed quartzose nodules, all work has been abandoned 

 since 1904. 



The pyrophyllite where it replaces rhyolite flows, as it does 

 almost exclusively, is a soft cryptocrystalline, light greenish-yellow 

 rock with a waxy luster and a good cleavage parallel to the schis- 

 tosity. In one case where it replaces the matrix of a volcanic 

 conglomerate it is a light brown and in another where it replaces 

 the matrix of a volcanic breccia it is cream colored. 



