igneous
Quartz-rich granitic pebble
Granite or granitic pegmatite; chiefly quartz (SiO₂), feldspar, and minor mica
AI-generated identification · may be incorrectTypically hardness 6–7, pale tan to cream, with a granular texture and vitreous to dull luster; interlocking quartz and feldspar crystals, with no obvious cleavage on the rounded surface. Exact identification is limited by the image.
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Physical properties
Typically hardness 6–7, pale tan to cream, with a granular texture and vitreous to dull luster; interlocking quartz and feldspar crystals, with no obvious cleavage on the rounded surface. Exact identification is limited by the image.
Formation & geological history
Formed when silica-rich magma slowly crystallized deep underground, generally in Precambrian to Phanerozoic continental crust; later weathering and transport rounded it into a pebble.
Uses & applications
Common granitic material is used for aggregate, building stone, countertops, and landscaping; attractive pieces may be collected but are not usually jewelry grade.
Geological facts
The tan color commonly reflects iron staining or weathered feldspar. A glassy, translucent grain that scratches glass suggests quartz; feldspar is usually opaque and shows cleavage.
Field identification & locations
Common in stream gravels, glacial deposits, and weathered bedrock worldwide. A fresh broken surface, hand lens, streak, hardness, and acid test would distinguish granite from quartzite, sandstone, or calcite-rich rock.
