igneous
Tumbled granite pebble
Granite, a coarse-grained felsic intrusive igneous rock composed mainly of quartz, feldspar, and mica
AI-generated identification · may be incorrectHardness is approximately 6–7 Mohs; the specimen is rounded and polished, with a mottled pink, cream, gray, and black color, granular texture, and generally dull to slightly vitreous luster. Its visible grains indicate interlocking crystalline structure with no cleavage as a whole rock, though feldspar and mica have cl…
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Physical properties
Hardness is approximately 6–7 Mohs; the specimen is rounded and polished, with a mottled pink, cream, gray, and black color, granular texture, and generally dull to slightly vitreous luster. Its visible grains indicate interlocking crystalline structure with no cleavage as a whole rock, though feldspar and mica have cleavage.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in continental crust, commonly during Precambrian to Phanerozoic intrusive events; this piece was later weathered and mechanically tumbled. Common source environments include mountain plutons, glacial gravels, and stream deposits.
Uses & applications
Used extensively as dimension stone, countertops, monuments, paving, aggregate, and building material; small polished pieces are sold as decorative stones and inexpensive collectibles.
Geological facts
The pink component is commonly potassium feldspar, gray translucent grains are quartz, and dark flecks are biotite or hornblende. A hand lens typically reveals the interlocking “salt-and-pepper” texture.
Field identification & locations
Identify it by its coarse, speckled texture and resistance to scratching; quartz and feldspar grains should be visible, unlike similarly colored basalt. Common worldwide, especially in continental mountain belts and glacial deposits.
