Rocks are usually grouped into three main groups&colon; igneous rocks, metamorphic rocks and sedimentary rocks. Mica is widely distributed and occurs in igneous, metamorphic and sedimentary regimes. Tuff can be classified as either sedimentary or igneous rock. It occurs as detrital grains in sedimentary rocks. Known as laccoliths, they formed when igneous rock protruded through cracks in the sedimentary rock. There are three major types of rock&colon; igneous, sedimentary, and metamorphic. These were of rock types including basalt, andesite, ignimbrite and sedimentary rock. These started with early layers of quartz rich sandstone derived from sedimentary and metasedimentary rocks. It becomes peat in good geochemical, sedimentary and tectonic conditions. The sedimentary and volcanic layers are folded and faulted. Magma was injected between layers of sedimentary rock, forming diabase sills. Geological correlation is the main tool for reconstructing the geometry of layering in sedimentary basins. About 10% of sedimentary rocks are limestones. Shungite may also occur as clasts within younger sedimentary rocks. It is primarily used in the study of sedimentary and layered volcanic rocks.