igneous
Weathered granite or granitic gneiss
Quartz–feldspar–mica aggregate; likely granite, possibly foliated gneiss
AI-generated identification · may be incorrectCoarse, irregularly granular specimen with pale gray feldspar/quartz, dark mica or amphibole, and orange-brown iron-oxide staining; likely Mohs 6–7, vitreous to dull luster, interlocking crystals, and no obvious cleavage as a whole rock.
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, irregularly granular specimen with pale gray feldspar/quartz, dark mica or amphibole, and orange-brown iron-oxide staining; likely Mohs 6–7, vitreous to dull luster, interlocking crystals, and no obvious cleavage as a whole rock.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep underground; gneiss forms when granitic rock is metamorphosed under high heat and pressure. The visible rusty coating reflects later weathering and oxidation, commonly over millions to billions of years.
Uses & applications
Used as crushed stone, aggregate, building stone, monuments, and countertops; attractive hand specimens have modest collecting value.
Geological facts
The broad pale grains and dark mineral patches are consistent with quartz, feldspar, and biotite or hornblende. Exact identification requires a fresh surface, hand lens, and ideally thin-section or mineral tests.
Field identification & locations
Common worldwide in continental crust and exposed in mountain belts, shields, and weathered boulder fields. Identify by testing glass scratching, observing interlocking light and dark grains, and checking for any planar foliation.
