Igneous intrusions of dolerite, felsite, lamprophyre and diorite of Palaeozoic age are encountered in places. The ring dyke is composite with both porphyritic granophyre and porphyritic felsite components. Felsite from Karnataka is being extensively used as a dimensional stone as well. The composition varies from rhyolite to felsite, with phenocrysts of alkali feldspar and mafic minerals. Felsite is a very fine-grained volcanic rock that may or may not contain larger crystals.