igneous
Rounded granite cobble
Granite; primarily quartz, feldspar, and biotite/hornblende
AI-generated identification · may be incorrectCoarse-grained, speckled pink-gray and black, with a dull to slightly sparkling luster; typical Mohs hardness 6–7, no prominent cleavage as a whole, and density about 2.6–2.8 g/cm³.
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Physical properties
Coarse-grained, speckled pink-gray and black, with a dull to slightly sparkling luster; typical Mohs hardness 6–7, no prominent cleavage as a whole, and density about 2.6–2.8 g/cm³.
Formation & geological history
Intrusive felsic igneous rock crystallized slowly from magma deep in Earth’s crust, commonly during Precambrian to Phanerozoic mountain-building; its rounded shape likely results from stream or glacial transport and abrasion.
Uses & applications
Used extensively as crushed stone, aggregate, paving, buildings, countertops, monuments, and landscaping; this small rounded specimen has minimal commercial value but may be useful as a teaching or collection sample.
Geological facts
Visible interlocking grains and pink potassium feldspar are characteristic of granite, though similar rocks such as granodiorite are possible from a photograph alone.
Field identification & locations
Identify it by its coarse interlocking quartz-feldspar-mica texture, lack of layering, and hardness; common in continental crust, riverbeds, glacial deposits, and granite terrains worldwide.
