igneous
Likely weathered granite or granitic gneiss
Granite: quartz + feldspar + mica; possibly gneiss if the faint banding is structural
AI-generated identification · may be incorrectCoarse-grained, mottled gray-brown specimen with pale mineral grains and darker mafic minerals; likely Mohs 6–7, vitreous to dull luster, granular crystal structure, and no obvious cleavage as a whole rock. Rounded edges suggest natural weathering or tumbling.
Identified More igneous →
Explore Likely 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-grained, mottled gray-brown specimen with pale mineral grains and darker mafic minerals; likely Mohs 6–7, vitreous to dull luster, granular crystal structure, and no obvious cleavage as a whole rock. Rounded edges suggest natural weathering or tumbling.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in the crust, commonly during Precambrian to younger continental mountain-building events; gneiss forms when granite is metamorphosed under high heat and pressure. Exact age cannot be determined from the image.
Uses & applications
Used as crushed aggregate, building stone, paving, monuments, and countertops; attractive pieces may be collected but are generally low-value.
Geological facts
Quartz and feldspar usually appear as light grains, while biotite or hornblende create dark flecks. A streak test is generally white, and the rock should not fizz with dilute hydrochloric acid.
Field identification & locations
Common in continental shields, mountain ranges, glacial deposits, and stream gravels worldwide. Identify with a hand lens, hardness testing, and checking for foliation or aligned mineral bands.
