Rocks are naturally formed, consolidated material composed
of grains of one or more minerals.
1) Igneous Rocks
Rocks that are formed or apparently formed from the solidification of a magma. Includes
intrusive or plutonic rocks, such as granite, and extrusive or volcanic rocks such as basalt.
2) Sedimentary Rocks
Rocks that are formed from (1) lithification of any type of sediment, (2) chemical
precipitation from solution, (3) consolidation of the remains of plants or animals.
3) Metamorphic Rocks
Rocks that are formed through the transformation of preexisting rock into texturally or
mineralogically distinct new rock as a result of high temperature, high pressure or both, but without
the rock melting in the process. The depth and temperature of the metamorphism define the grade of
metamorphism.
