igneous
Rounded granite cobble
Granite, a coarse-grained felsic intrusive igneous rock
AI-generated identification · may be incorrectPinkish-tan, granular surface with likely quartz, feldspar, and minor mica; minerals are typically Mohs 6–7, with vitreous quartz and cleavage in feldspar. The cobble’s smooth oval shape reflects prolonged abrasion; exact composition cannot be confirmed from the image alone.
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Physical properties
Pinkish-tan, granular surface with likely quartz, feldspar, and minor mica; minerals are typically Mohs 6–7, with vitreous quartz and cleavage in feldspar. The cobble’s smooth oval shape reflects prolonged abrasion; exact composition cannot be confirmed from the image alone.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in the crust; its age depends on its source and may range from millions to billions of years. The rounded form likely developed through river or beach transport, or mechanical tumbling.
Uses & applications
Granite is widely used as building and paving stone, countertops, monuments, and landscaping rock; this cobble is mainly decorative.
Geological facts
Granite is an assemblage of minerals, not a single mineral, and its pink color commonly comes from potassium feldspar.
Field identification & locations
Look for visible interlocking grains, pale quartz, pink or white feldspar, and scattered dark minerals; granite occurs worldwide and rounded cobbles are common in rivers and glacial deposits. A loose landscaping-size specimen typically has little collector value, around $1–$20.
