Natural cut stone as a building material is derived from quarried rock; divided into three types, the classifications relate to how the rock was formed geologically. Igneous rock, such as granite, is formed by the crystallization and cooling of molten magma. It forms the bases of continents and mountains ranges, and is relatively hard and homogenous.
Sedimentary rock is created by a more complicated progression when weather and water movement erodes igneous rocks, forming gravel, sand and silt. These are deposited on the bottoms of oceans, lakes and river beds, along with minerals from sea water and marine organisms.