igneous
Weathered granite or granitic gneiss pebble
Granite, chiefly quartz (SiO₂), feldspar, and biotite/hornblende; exact identification is uncertain from the image
AI-generated identification · may be incorrectCoarse, interlocking crystalline texture with pale pink/tan feldspar and dark biotite or amphibole; typically Mohs 6–7, vitreous to dull luster, no prominent cleavage as a whole, and specific gravity about 2.6–2.8.
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Physical properties
Coarse, interlocking crystalline texture with pale pink/tan feldspar and dark biotite or amphibole; typically Mohs 6–7, vitreous to dull luster, no prominent cleavage as a whole, and specific gravity about 2.6–2.8.
Formation & geological history
Formed by slow cooling of silica-rich magma deep in the crust, generally during Precambrian or younger continental mountain-building; the rounded shape indicates later stream or glacial transport and weathering.
Uses & applications
Used as crushed stone, building stone, countertops, monuments, and aggregate; this small rounded specimen is mainly suitable for collecting or decorative display.
Geological facts
The dark portion may represent a mafic-rich enclave or band, while the pale area is feldspar-rich granite. A true gneiss would show mineral alignment or compositional banding, not clearly evident here.
Field identification & locations
Look for visible quartz, pink/white feldspar, and black mica or amphibole in an interlocking texture; a glassy streak or strong fizz would suggest another material. Common worldwide, especially in continental shields and mountain belts.
