HYDRON SILICATES IN ROCKS OF CONCEPTION BAY 135 



to one-half of the rock. Paralleling this zone at a distance of about 

 20 feet is a pyrophyllite vein 18 feet in width with a 3-foot stringer 

 and many spheroids of altered rhyolite wall rock in its central 

 portion. The spheroids vary from an inch to a foot in diameter, but 

 average about 4 inches. A lenticular or elliptical structure (Fig. 2) 

 characterizes the rhyolite adjacent to the vein and the schistose 

 matrix of the lenses or ellipsoids is partially pyrophyllitized. A 

 few hundred feet north of here a light brownish pyrophyllite is 



Fig. 3. — View of portion of pyrophyllite vein, showing intermingling of pyrophyl- 

 lite and country rock. p= pyrophyllite; q = quartz-pyrophyllite. 



found replacing portions of the matrix of a white rhyolite con- 

 glomerate. 



DESCRIPTION OF PINITE 



At Manuels the pinite is a relatively rare constituent and is 

 interesting only from the viewpoint of its origin. It is best 

 exhibited at talc prospect 5 and at a point marked 228 D 1 on the 

 map. Fig. 4 is a photograph taken at this latter locality and repre- 

 sents the matrix of a spherulitic rhyolite (228 D 1 h) replaced by 

 dark-colored pinite. The spherulites here average about 1 inch 



