Granite is a fully crystallized, homogeneous-grained or porphyritic intrusive rock. Granite is a rock composed primarily of quartz and feldspar crystals. It is classified according to the composition and quantity of feldspars and non-ferrous minerals.
Granite is divided into two groups: calcium-alkaline or normal granite and alkaline granite. The mineralogical composition of granite is normal: alkaline feldspar consists of orthoclase or microcline, plagioclase-oligoclase-andesine, quartz, colored minerals - biotite, hornblende, muscovite. In some cases, pyroxene is observed. When feldspar consists only or mostly of plagioclase, it is called plagiogranite, and when it contains no colored minerals or in very small quantities, it is called alaskite. Alkaline granite consists of alkaline feldspar microperthite, microcline-microperthite, anorthoclase, plagioclase-albite, and non-ferrous minerals - alkaline amphiboles and alkaline pyroxenes (riebeckite, arfvedsonite, aegirine). The areas occupied by calc-alkaline intrusions reach several hundred and even thousands of km², and alkaline granites form small reserves.
By origin, granite is divided into three groups:
a) granite formed as a result of crystallization of granitic magma;
b) granite with last differentials of hybridized basaltic magma;
c) granite formed as a result of regional metasomatism. The latter type of granite is widespread in Archean and Proterozoic rocks