igneous
Tumbled granite pebble
Granite, mainly quartz (SiO₂), feldspar, and minor biotite/hornblende
AI-generated identification · may be incorrectCoarse-grained crystalline texture with white-gray feldspar and quartz plus dark mineral specks; vitreous to dull luster, no prominent cleavage as a whole, Mohs hardness about 6–7, and specific gravity roughly 2.63–2.75. Its egg-like shape indicates natural or deliberate tumbling/polishing.
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Physical properties
Coarse-grained crystalline texture with white-gray feldspar and quartz plus dark mineral specks; vitreous to dull luster, no prominent cleavage as a whole, Mohs hardness about 6–7, and specific gravity roughly 2.63–2.75. Its egg-like shape indicates natural or deliberate tumbling/polishing.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in continental crust, commonly during Precambrian to Phanerozoic mountain-building events; this specimen was later weathered and rounded. Exact age and locality cannot be determined from the image.
Uses & applications
Used extensively as dimension stone, countertops, monuments, aggregate, and landscaping; small polished pieces are sold as decorative or educational specimens.
Geological facts
The dark grains are likely biotite or amphibole, while the pale matrix is mostly feldspar and quartz. Granite’s visible interlocking crystals distinguish it from many fine-grained pale rocks.
Field identification & locations
Identify by interlocking visible crystals, pale feldspar/quartz, scattered dark mica or amphibole, and lack of layering or vesicles; common in continental mountain belts worldwide. A scratch test should show resistance to a steel knife, though testing may damage the polish.
