igneous
Weathered granite or granitic pebble
Granite; quartz–feldspar–mica aggregate
AI-generated identification · may be incorrectCoarse-grained, brown-gray and mottled, with a dull to slightly vitreous luster; likely quartz, feldspar, and dark mica or iron-oxide staining. Hardness is approximately Mohs 6–7; no consistent cleavage as a whole rock, though feldspar may cleave; specific gravity about 2.6–2.7.
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Physical properties
Coarse-grained, brown-gray and mottled, with a dull to slightly vitreous luster; likely quartz, feldspar, and dark mica or iron-oxide staining. Hardness is approximately Mohs 6–7; no consistent cleavage as a whole rock, though feldspar may cleave; specific gravity about 2.6–2.7.
Formation & geological history
Formed when silica-rich magma slowly crystallized deep underground, producing interlocking crystals; its exact geological age cannot be determined visually and may range from Precambrian to younger. The rounded shape and brown coating indicate prolonged weathering and transport.
Uses & applications
Common granite is used as crushed aggregate, building stone, paving, monuments, and landscaping material; this small specimen has mainly educational or decorative value.
Geological facts
Granite’s visible speckling reflects slow cooling, unlike fine-grained volcanic rocks. Iron-bearing minerals commonly weather to reddish-brown oxides.
Field identification & locations
Look for interlocking visible quartz, pale feldspar, and darker mica grains, plus a hard, scratch-resistant surface; acid testing is generally negative. Similar pebbles occur in stream gravels and glacial deposits worldwide.
