Polarised light micrograph of granite from the Fichtel Mountains, Germany. Granite is an igneous rock with between 20% and 60% quartz by volume, and with at least 35% of the total feldspar being alkali feldspar. Granite is more common in continental crust than in oceanic crust. It is crystallised from felsic melts, which are less dense than mafic rocks and thus tend to ascend toward the surface. Magnification: x30 when printed at 15 centimetres wide.