igneous
Granite cobble
Granite, a coarse-grained felsic intrusive igneous rock composed mainly of quartz, feldspar, and mica
AI-generated identification · may be incorrectGray, speckled, granular surface with interlocking crystals and no visible layering; typical Mohs hardness is about 6–7. Mineral proportions and specific gravity vary, commonly around 2.6–2.8.
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Physical properties
Gray, speckled, granular surface with interlocking crystals and no visible layering; typical Mohs hardness is about 6–7. Mineral proportions and specific gravity vary, commonly around 2.6–2.8.
Formation & geological history
Formed as silica-rich magma cooled slowly underground, allowing visible crystals to grow; its age cannot be determined from the image and depends on its source. The rounded shape likely results from prolonged abrasion in water or sediment transport.
Uses & applications
Granite is used for building stone, paving, countertops, monuments, and landscaping; this small cobble is mainly suitable for collecting or decoration.
Geological facts
Granite is a rock rather than a single mineral; its quartz and feldspar grains give it its characteristic speckled appearance.
Field identification & locations
Look for interlocking light and dark mineral grains, especially glassy quartz and feldspar, and test hardness against glass. Granite occurs widely in continental crust and is common in stream and beach gravels.
