igneous
Tumbled granite
Granite, chiefly quartz, alkali feldspar, plagioclase, and biotite/hornblende
AI-generated identification · may be incorrectCoarse-grained, mottled gray, cream, pink, black, and greenish-brown appearance with a vitreous-to-dull luster; hardness about 6–7 Mohs, granular crystal structure, no prominent cleavage as a whole, and specific gravity around 2.63–2.75.
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Physical properties
Coarse-grained, mottled gray, cream, pink, black, and greenish-brown appearance with a vitreous-to-dull luster; hardness about 6–7 Mohs, granular crystal structure, no prominent cleavage as a whole, and specific gravity around 2.63–2.75.
Formation & geological history
An intrusive igneous rock formed by slow cooling and crystallization of silica-rich magma deep in Earth’s crust, commonly during Precambrian to younger continental mountain-building events. This specimen has been rounded and polished by tumbling.
Uses & applications
Used for countertops, building stone, monuments, aggregate, landscaping, and decorative polished stones; typically low individual collector value.
Geological facts
The visible interlocking crystals indicate slow underground cooling rather than volcanic eruption. Greenish areas may reflect altered feldspar or minor chlorite/amphibole.
Field identification & locations
Identify it by its coarse interlocking grains, abundant light feldspar/quartz, and scattered dark mica or amphibole; it is not likely to scratch glass if unusually weathered, though fresh granite generally can. Common worldwide, especially in continental shields and mountain ranges.
