What are the three rock types of science?

Answer 1

IGNEOUS refers to rocks that originate in the interior of the Earth, and include the various volcanic types and the granite group of rocks. There is a 1:1 correspondence between the granite types of rock, and the volcanic ones - it depends upon whether they have been melted or not. Granites usually have well differentiated crystals, and are hard.

SEDIMENTARY rocks are those that have result from the weathering of the above igneous rocks, and in general are deposited as fine-grained sediments at sea, and this will eventually form rocks.

METAMORPHIC rocks are generally formed from sedimentary rocks that have been subjected to heat and pressure. Consequently, the mineral assembly will differ from that of the sedimentary, new minerals will be formed, and shear and folding are common. The degree of metamorphism varies depending on the burial pressure and temperatures. In the extreme of melting, then granites will result if the cooling is very slow, or volcanics will form if the rock is ejected in the molten state.

Marble is a curious metamorphic rock in that it may be formed from the hard bodies of tiny marine animals, but with a low degree of metamorphism, often fossils may still be recognized. At extreme metamorphism, it will become a matrix mainly of CaCO3.