Charnockite

It is a greyish medium to fine grained rock comprised of yellowish grey feldspar, pale bluish grey quartz and dark glistening grains of hypersthene. It is an acid rock over saturated with silica. It is collected from Pallavaram, Chennai. This rock is named after Job Charnock, an East India company clerk and founder of Calcutta, whose tombstone is made of charnockite.