Andesite A volcanic rock that is made up of light colored minerals and dark minerals. It is fine grained and has a chemical composition intermediate to basalt and rhyolite. Breccia A rock composed of angular rock fragments cemented together. This is the basic difference between breccia and conglomerates which have rounded fragments. Coal Formed from forest type vegetation that accumulated in swamps to form peat beds and subsequently subjected to great pressure for a long period of time to compact.
Black coal contains less ash and woody fragments.
A mass of rounded particles of various sizes cemented together. Usually found in hilly terrain with a fast flowing river. Dolomite This rock is thought to have been formed by the action of sea water on limestone, which caused some of the calcium to be replaced by magnesium. Gneiss Has irregular banded appearance and sometimes resembles a granite. It is the final stage before a rock melts to form a granite.