In some granites, individual crystals are larger than the groundmass (porphyrys). Granites primarily comprises orthoclase and plagioclase feldspars, quartz, hornblende, muscovite and/or biotite micas, with minor accessory minerals such as magnetite, garnets, zircon and apatite. Rarely, a pyroxene is present. Very rarely, iron-rich olivine, fayalite, occurs.
Granites are classified according to the QAPF diagram for granitoids and phaneritic foidolites (plutonic rocks) that compares the percentages of quartz, alkali feldspar (orthoclase, sanidine, or microcline) and plagioclase feldspar.
As a plutonic rock, granite is often exposed in weathered tors, dykes and as massive batholiths.
Labels: batholith, biotite, continental crust, dyke, feldspar, felsic, granite, hornblende, igneous rock, mica, muscovite, orthoclase, plagioclase, plutonic, porphyry, Precambrian rocks, QAPF, quartz, tor