igneous
Rounded granite cobble
Granite; chiefly quartz, alkali feldspar, plagioclase, and biotite/hornblende
AI-generated identification · may be incorrectCoarse-grained, speckled white-gray rock with pinkish-brown staining; interlocking crystals and granular texture, generally vitreous to dull luster. Hardness about 6–7 Mohs; no obvious cleavage as a whole; density roughly 2.6–2.7 g/cm³. Its spherical shape is natural or abrasion-produced, rather than a crystal form.
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Physical properties
Coarse-grained, speckled white-gray rock with pinkish-brown staining; interlocking crystals and granular texture, generally vitreous to dull luster. Hardness about 6–7 Mohs; no obvious cleavage as a whole; density roughly 2.6–2.7 g/cm³. Its spherical shape is natural or abrasion-produced, rather than a crystal form.
Formation & geological history
Slow cooling of silica-rich magma several kilometers underground formed the granite, commonly during Precambrian to Phanerozoic intrusive events. Rounding likely resulted from stream, beach, or glacial abrasion, with surface weathering producing the brown staining.
Uses & applications
Granite is widely used for building stone, countertops, paving, monuments, aggregate, and landscaping. This rounded specimen has modest educational or decorative value.
Geological facts
The visible grains are individual interlocking minerals: translucent quartz, pale feldspars, and darker mafic minerals. Pink or rusty tones commonly reflect potassium feldspar and iron-oxide weathering.
Field identification & locations
Identify it by its coarse “salt-and-pepper” texture, hardness, and lack of layering or foliation; it should resist scratching from a steel knife but may be scratched by quartz. Common worldwide near exposed batholiths and glacial or river deposits.
