...exceeding the size of large paving stones, probably owing to the somewhat brittle nature of the rock. Under the microscope the greater part of the rock is seen to consist of an inter-growth of quartz and felspar in a variety of forms from fine to coarse — *"The...

...porous light-gray rock of lithoidal character, mixed to a certain extent locally with dark grayish-green glassy portions. Both the lithoidal and glassy portions...extinguish both parallel and oblique. Whether they arc actually intergrown with quartz can not positively be asserted. The outer portion of the spherulite...