igneous
Coarse-grained granite or granitic gneiss
Granite; primarily quartz, potassium feldspar, plagioclase, and biotite/hornblende
AI-generated identification · may be incorrectHardness about 6–7 Mohs; light gray to pinkish with black, silver, and white grains, vitreous to dull luster, interlocking crystals, and no prominent cleavage as a whole. The visible foliation or banding may indicate gneiss rather than undeformed granite.
Identified More igneous →
Explore Coarse-grained granite or granitic gneiss in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness about 6–7 Mohs; light gray to pinkish with black, silver, and white grains, vitreous to dull luster, interlocking crystals, and no prominent cleavage as a whole. The visible foliation or banding may indicate gneiss rather than undeformed granite.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep underground, commonly during Precambrian to Mesozoic mountain-building events; gneiss forms when such rock is intensely metamorphosed under high temperature and pressure.
Uses & applications
Widely used for countertops, monuments, building stone, aggregate, and landscaping; attractive polished pieces may be collected, but this specimen appears ordinary and unpolished.
Geological facts
Large visible crystals indicate slow cooling, while aligned dark minerals or streaks suggest metamorphic deformation. Quartz is typically glassy and gray, feldspar white or pink, and biotite black and flaky.
Field identification & locations
Identify it by its coarse interlocking quartz–feldspar–mica texture; gneiss shows distinct mineral banding or alignment. Common worldwide in continental crust and exposed mountain belts.
