Granites are usually classified as igneous rocks obtained from molten masses or magmas. There is evidence that the origin of some granites may be attributed to regional metamorphism of pre-existing rocks; rearrangement and re-crystallization taking place without a liquid or molten stage.
Granite is classified into three different groups as follows:
Fine Grain: Fine grain granites are those in which the feldspar crystals average about 1/16 to 1/8″ in diameter.
Medium Grain: In the medium grain granites the feldspar crystals average about 1/4″ in diameter.
Coarse Grain: The feldspar crystals in course grain granites average 1/2″ and greater in diameter or several centimeters in maximum dimension. Coarse grain granites have a lower density.