igneous
Granite (likely biotite granite)
Coarse-grained plutonic rock composed mainly of quartz, feldspar, and biotite mica
AI-generated identification · may be incorrectTypically gray, speckled, and granular with a glassy quartz luster; hardness about 6–7 Mohs, no consistent cleavage as a rock, and specific gravity around 2.6–2.7. The dark flakes are probably biotite or hornblende.
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Physical properties
Typically gray, speckled, and granular with a glassy quartz luster; hardness about 6–7 Mohs, no consistent cleavage as a rock, and specific gravity around 2.6–2.7. The dark flakes are probably biotite or hornblende.
Formation & geological history
Forms when silica-rich magma cools slowly deep underground, producing visible interlocking crystals. Most granite formed during ancient Precambrian to Phanerozoic continental magmatic events; the exact age cannot be determined from the image.
Uses & applications
Widely used as building stone, countertops, monuments, paving, aggregate, and decorative specimens; small ordinary fragments have little jewelry value.
Geological facts
Granite is a rock rather than a single mineral, and its crystal size records slow underground cooling. Weathering commonly separates feldspar and creates a rough, granular surface.
Field identification & locations
Identify it by the visible interlocking grains: pale or pink feldspar, translucent gray quartz, and black mica/hornblende. Common worldwide, especially in continental mountain belts; a fresh surface and hand lens improve identification.
