igneous
Weathered granitoid pebble
Granite or granodiorite, composed mainly of quartz, feldspar, and mica/amphibole
AI-generated identification · may be incorrectHardness about 6–7 Mohs; pale gray-white with dark mineral flecks, granular texture, and dull to slightly glassy luster. No obvious cleavage as a rock; individual feldspar crystals may show cleavage.
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Physical properties
Hardness about 6–7 Mohs; pale gray-white with dark mineral flecks, granular texture, and dull to slightly glassy luster. No obvious cleavage as a rock; individual feldspar crystals may show cleavage.
Formation & geological history
An intrusive igneous rock that crystallized slowly from magma deep underground, typically millions to billions of years ago, then weathered into a rounded pebble. Exact identification and age require a fresh surface or laboratory testing.
Uses & applications
Commonly used as crushed aggregate, building stone, countertops, monuments, and landscaping material; this small weathered piece has negligible commercial value.
Geological facts
The visible dark grains are likely biotite mica or amphibole, while the light grains are feldspar and quartz. Surface weathering can obscure the original crystal texture.
Field identification & locations
Common worldwide, especially in continental shields, mountain belts, and glacial deposits. A fresh broken surface, acid test, hand lens, and hardness comparison help distinguish it from similar gneiss or quartz-rich rock.
