igneous
Rounded granite pebble
Granite, chiefly quartz, feldspar, and mica; possibly granodiorite
AI-generated identification · may be incorrectFine- to medium-grained, gray and speckled with low vitreous-to-dull luster; hardness about 6–7 Mohs, no obvious cleavage as a whole, and typical specific gravity 2.63–2.75. Its smooth elongated shape reflects abrasion rather than crystal form.
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Physical properties
Fine- to medium-grained, gray and speckled with low vitreous-to-dull luster; hardness about 6–7 Mohs, no obvious cleavage as a whole, and typical specific gravity 2.63–2.75. Its smooth elongated shape reflects abrasion rather than crystal form.
Formation & geological history
Formed by slow crystallization of silica-rich magma deep in the continental crust, commonly Precambrian to Phanerozoic in age, then exposed and rounded by stream, beach, or glacial transport.
Uses & applications
Granite is widely used for building stone, countertops, paving, aggregate, and monuments; this small waterworn specimen has mainly educational or decorative value.
Geological facts
The visible salt-and-pepper texture comes from interlocking quartz and feldspar grains with darker biotite or hornblende. The exact identification could be granodiorite if plagioclase dominates over potassium feldspar.
Field identification & locations
Look for interlocking grains, abundant pale feldspar/quartz, dark mica or amphibole, and resistance to scratching; quartz may scratch glass, while dilute acid should not fizz. Common worldwide, especially in continental shields and mountain belts.
