igneous
Tumbled granite or granitic gneiss
Granite: quartz, feldspar, and mica; possibly foliated gneiss
AI-generated identification · may be incorrectCoarse, interlocking grains with gray, pink, white, and dark mineral patches; vitreous to dull luster, no obvious cleavage as a whole, and Mohs hardness about 6–7. The rounded shape indicates tumbling or natural stream abrasion.
Identified More igneous →
Explore Tumbled granite or granitic gneiss in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Coarse, interlocking grains with gray, pink, white, and dark mineral patches; vitreous to dull luster, no obvious cleavage as a whole, and Mohs hardness about 6–7. The rounded shape indicates tumbling or natural stream abrasion.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in the crust; gneiss forms when granitic rock is intensely metamorphosed. Such rocks commonly formed during ancient Precambrian to Paleozoic mountain-building events.
Uses & applications
Used as crushed stone, aggregate, building stone, countertops, monuments, and landscaping material; tumbled pieces are mainly decorative or educational.
Geological facts
The light grains are likely quartz and feldspar, while dark grains may be biotite, amphibole, or pyroxene. Mineral proportions and texture suggest granite more strongly than a single-mineral specimen.
Field identification & locations
Identify it by its visibly interlocking, multicolored grains and lack of glassy or layered sedimentary texture; a streak test is usually white, and quartz grains resist scratching by steel. Common worldwide, especially in old continental shields and mountain belts.
