igneous
Weathered granitic rock fragment
Granitoid, likely biotite granite or granodiorite
AI-generated identification · may be incorrectCoarse, speckled texture with pale feldspar/quartz and dark biotite or amphibole; earthy brown-gray weathering, dull to weakly vitreous luster, and no obvious cleavage. Typical hardness is about 6–7 Mohs; specific gravity approximately 2.6–2.8.
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Physical properties
Coarse, speckled texture with pale feldspar/quartz and dark biotite or amphibole; earthy brown-gray weathering, dull to weakly vitreous luster, and no obvious cleavage. Typical hardness is about 6–7 Mohs; specific gravity approximately 2.6–2.8.
Formation & geological history
Formed when silica-rich magma slowly crystallized underground, commonly during Precambrian to Phanerozoic continental crust formation; surface weathering produced the rusty coating and rough texture.
Uses & applications
Used as crushed stone, aggregate, building stone, monuments, and dimension stone; this small weathered fragment has negligible jewelry or commercial value.
Geological facts
The visible grain size indicates slow cooling at depth rather than volcanic eruption. Iron-bearing biotite or amphibole commonly oxidizes to the orange-brown coloration.
Field identification & locations
Identify it by interlocking visible grains of quartz, feldspar, and dark mica/amphibole; a glassy streak or fizzing with dilute acid would suggest another material. Granites and granodiorites are widespread on continental shields and mountain belts worldwide.
