igneous
Polished river pebble, likely granite or granitic gneiss
Quartz–feldspar–mica aggregate; possibly biotite granite (compositionally near granite)
AI-generated identification · may be incorrectHardness about 6–7 Mohs; rounded, gray-tan, fine-to-medium crystalline texture with a subdued sparkly luster from mica and quartz. No obvious cleavage is visible; specific gravity likely 2.6–2.8.
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Physical properties
Hardness about 6–7 Mohs; rounded, gray-tan, fine-to-medium crystalline texture with a subdued sparkly luster from mica and quartz. No obvious cleavage is visible; specific gravity likely 2.6–2.8.
Formation & geological history
Likely formed as intrusive felsic rock when magma slowly crystallized deep underground, then was weathered and rounded by transport in a river or beach. Its exact geological age and identity cannot be determined from the photograph alone.
Uses & applications
Commonly used as landscaping stone, decorative gravel, and a polished ornamental pebble; not typically valuable as a gemstone.
Geological facts
The rounded shape and smooth surface indicate prolonged abrasion, while the scattered glitter likely reflects mica flakes. It could also be a weathered metamorphic rock such as gneiss, requiring a close examination of banding and mineral grains.
Field identification & locations
Look for interlocking quartz and feldspar grains, black or silvery mica, and hardness sufficient to scratch glass; a streak, acid test, and fresh broken surface would improve identification. Common worldwide in river gravels and glacial deposits.
