igneous
Quartz-rich granite or granitic pegmatite fragment
Granite; primarily quartz (SiO₂), feldspar, and mica
AI-generated identification · may be incorrectCoarse, crystalline texture with translucent gray quartz, pale feldspar, and possible reflective mica; Mohs hardness about 6–7, vitreous quartz luster, and no obvious cleavage in quartz. The image is insufficient for a precise mineral identification.
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Physical properties
Coarse, crystalline texture with translucent gray quartz, pale feldspar, and possible reflective mica; Mohs hardness about 6–7, vitreous quartz luster, and no obvious cleavage in quartz. The image is insufficient for a precise mineral identification.
Formation & geological history
Formed when silica-rich magma slowly cooled underground, allowing visible crystals to grow; most examples formed hundreds of millions to billions of years ago. Pegmatitic varieties crystallized from late, water-rich magma and may contain unusually large crystals.
Uses & applications
Common granite is used for countertops, monuments, aggregate, and building stone; attractive small pieces are collected but generally have little commercial value.
Geological facts
Quartz appears glassy or translucent, feldspar is commonly white or pink, and mica produces shiny flakes. A streak, hardness test, and close inspection of crystal boundaries would distinguish it from quartzite or weathered concrete.
Field identification & locations
Common worldwide in continental crust, especially exposed in mountain belts and old shields. Estimated value: $1–$10 for an ordinary loose fragment, or $10–$50 if unusually crystalline or pegmatitic.
