igneous
Rounded granitic pebble
Granite or granitic gneiss; chiefly quartz, feldspar, and mica
AI-generated identification · may be incorrectHardness about 6–7 Mohs; coarse-grained, speckled gray, white, and black, with a vitreous-to-dull luster. Interlocking crystals are visible, and cleavage occurs mainly in feldspar and mica rather than the whole pebble.
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Physical properties
Hardness about 6–7 Mohs; coarse-grained, speckled gray, white, and black, with a vitreous-to-dull luster. Interlocking crystals are visible, and cleavage occurs mainly in feldspar and mica rather than the whole pebble.
Formation & geological history
Formed by slow cooling of silica-rich magma deep underground, likely hundreds of millions to billions of years ago; later erosion rounded it into a pebble. The image alone cannot distinguish granite from foliated granitic gneiss with certainty.
Uses & applications
Commonly used as crushed aggregate, building stone, monuments, countertops, and landscaping gravel; this small specimen has mainly educational or collector value.
Geological facts
Quartz grains are typically glassy and translucent, feldspar is white or pink, and mica appears as dark reflective flakes. Its rounded shape indicates transport by water, ice, or long-term surface erosion.
Field identification & locations
Look for visible interlocking quartz, feldspar, and dark mica, no vesicles, and a hard surface that resists scratching by steel. Common in streambeds, glacial deposits, and areas near granite or gneiss outcrops.
