igneous
Likely weathered granite or granitic gneiss fragment
Quartz–feldspar–mica aggregate; possibly biotite granite or granitoid gneiss
AI-generated identification · may be incorrectCoarse, speckled gray-tan material with visible dark mica, pale feldspar, and probable quartz; typically Mohs 6–7, vitreous to dull luster, granular texture, and no prominent cleavage as a whole rock. The small, irregular specimen appears weathered and may contain darker biotite or amphibole.
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Physical properties
Coarse, speckled gray-tan material with visible dark mica, pale feldspar, and probable quartz; typically Mohs 6–7, vitreous to dull luster, granular texture, and no prominent cleavage as a whole rock. The small, irregular specimen appears weathered and may contain darker biotite or amphibole.
Formation & geological history
Formed by slow crystallization of silica-rich magma deep in the crust, generally during Precambrian to Phanerozoic continental plutonism; gneissic varieties were later altered by high-grade metamorphism. Exact age and identity require a fresh surface or laboratory testing.
Uses & applications
Granite is widely used for construction stone, countertops, monuments, aggregate, and dimension stone; small fragments have modest geological-collection value.
Geological facts
The interlocking crystals indicate slow cooling rather than volcanic eruption. Dark mica commonly gives granite its black flecks and may weather out, leaving a rough surface.
Field identification & locations
Look for interlocking pale feldspar, translucent gray quartz, and black mica; a glassy streak or acid reaction would suggest another material. Common worldwide, especially in continental shields and mountain belts.
