Granite is the best-known of the plutonic igneous rocks worldwide, and one of the most common. The granites are composed of 40-70% potassium feldspar, 10-30% quartz, 10-30% plagioclase and 3-10% biotite, sometimes with a few percent of other minerals, e.g. hornblende.
The granites and granodiorites are frequently very colourful, being greyish, reddish, brown or greenish in tone. It is common for commercial purposes to refer to granodiorites, diorites, gabbros, diabases and highly patterned migmatites and gneisses as granites.
The granites vary in their technical properties, mainly according to the grain size of the minerals contained in them and the binding and orientation of the grains. Granite is a hard, expressive natural building stone of excellent durability.
Granodiorite is closely related to granite, differing from it in possessing slightly less potassium feldspar and more plagioclase. The granodiorites are generally darker in colour on account of the presence of black hornblende.