igneous
Weathered granite or granitic gneiss
Granite, chiefly quartz–feldspar–mica; possible gneissic variant
AI-generated identification · may be incorrectCoarse, uneven granular texture with tan/cream feldspar, darker minerals, and weak foliation; likely Mohs 6–7, vitreous to dull luster, no obvious cleavage as a whole, and specific gravity about 2.6–2.8.
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Physical properties
Coarse, uneven granular texture with tan/cream feldspar, darker minerals, and weak foliation; likely Mohs 6–7, vitreous to dull luster, no obvious 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, likely during Precambrian to Phanerozoic continental crust formation; surface weathering has rounded and stained the specimen.
Uses & applications
Commonly used as crushed stone, aggregate, building stone, monuments, countertops, and landscaping material; this irregular specimen has little jewelry value.
Geological facts
The tan-brown coloration is commonly produced by oxidation and weathering of iron-bearing biotite or other mafic minerals. A fresh broken surface would better reveal quartz, feldspar, and mica grains.
Field identification & locations
Look for interlocking visible grains: glassy gray quartz, pale feldspar, and black mica or hornblende; granite lacks the strong layering typical of schist or gneiss. Common worldwide in continental mountain belts and basement exposures.
