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.

Dunite

    It is mono mineralic rock and consists essentially yellowish green olivine. It is a pale yellowish green, fine grained granular rock. This specimen was collected from Chalk hills, Salem.

^Syenite

    The syenite is a coarse grained igneous rock characterised by the presence of feldspar. Typical ferro magnesian minerals such as hornblende, biotite, augite, zircon and apatite are common accessory minerals.