igneous
Weathered granite or granitic gneiss
Granite; primarily quartz, feldspar, and mica (possibly gneiss if the faint banding is structural)
AI-generated identification · may be incorrectCoarse, mottled gray-brown surface with pale feldspar/quartz and darker biotite; quartz hardness ~7, feldspar ~6, vitreous to dull luster, interlocking crystalline texture, and no obvious cleavage at the rock scale.
Identified More igneous →
Explore Weathered granite or granitic gneiss in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Coarse, mottled gray-brown surface with pale feldspar/quartz and darker biotite; quartz hardness ~7, feldspar ~6, vitreous to dull luster, interlocking crystalline texture, and no obvious cleavage at the rock scale.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in the crust, commonly during Precambrian to Phanerozoic mountain-building; surface weathering has darkened and softened this specimen. If foliated, it may represent metamorphosed granite (gneiss).
Uses & applications
Widely used as dimension stone, building facades, countertops, paving, monuments, and crushed aggregate; this weathered outdoor piece has little commercial collector value.
Geological facts
Granite’s visible speckling reflects crystals that cooled over thousands to millions of years. Chemical weathering commonly produces rusty brown staining from oxidation of iron-bearing minerals.
Field identification & locations
Identify it by the visible interlocking grains of light quartz/feldspar and dark mica, lack of rounded sedimentary layers, and hardness sufficient to scratch glass; a fresh broken surface would be more diagnostic. Common worldwide, especially in continental shields and mountain belts.
