igneous
Likely weathered granite or granitic gneiss fragment
Quartz–feldspar–biotite aggregate; possibly foliated granitic gneiss
AI-generated identification · may be incorrectCoarse, irregular gray-brown specimen with visible light feldspar/quartz and darker mica or mafic grains; typically Mohs 6–7, vitreous quartz and dull feldspar luster, granular texture, no prominent cleavage as a whole, and specific gravity about 2.6–2.8.
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Physical properties
Coarse, irregular gray-brown specimen with visible light feldspar/quartz and darker mica or mafic grains; typically Mohs 6–7, vitreous quartz and dull feldspar luster, granular texture, no prominent cleavage as a whole, and specific gravity about 2.6–2.8.
Formation & geological history
Likely crystallized slowly from silica-rich magma deep in the crust, or represents metamorphosed granite; Precambrian to younger ages are possible but cannot be determined from the image. Weathering has produced the brown surface coating.
Uses & applications
Granite and gneiss are used as crushed aggregate, road stone, building stone, monuments, and occasionally decorative slabs; this small fragment has negligible commercial value.
Geological facts
The image does not show enough detail for a definitive species-level identification. A fresh broken surface, hand lens, streak, and tests for quartz, feldspar, and mica would improve confidence.
Field identification & locations
Look for interlocking grains: glassy gray quartz, pale cleavage-faced feldspar, and shiny dark mica; gneiss may show compositional banding. Common worldwide, especially in continental mountain belts and exposed basement rocks.
