igneous
Granite (likely biotite-bearing granite)
Coarse-grained felsic intrusive rock, mainly quartz, feldspar, and dark biotite or amphibole
AI-generated identification · may be incorrectSpeckled gray, black, and pink; visible interlocking crystals with a granular texture. Typical mineral hardness: quartz 7, feldspar 6, biotite 2.5–3; granite has no consistent cleavage.
- Hardness
- quartz 7, feldspar 6, biotite 2
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Physical properties
Speckled gray, black, and pink; visible interlocking crystals with a granular texture. Typical mineral hardness: quartz 7, feldspar 6, biotite 2.5–3; granite has no consistent cleavage.
Formation & geological history
Magma cooled slowly underground, allowing crystals to grow. Granite forms in continental crust across many geological ages; the photo alone cannot establish this specimen’s age.
Uses & applications
Commonly used as building and paving stone, countertops, monuments, and landscaping material; attractive pieces may be collected.
Geological facts
The contrasting light and dark grains reflect different minerals, commonly quartz and feldspar alongside biotite or amphibole.
Field identification & locations
Look for interlocking, visible grains and a mix of light quartz/feldspar with dark minerals; this hand-sized specimen appears granite-like, though a clear identification may require closer inspection. Granite occurs widely in continental mountain belts and exposed plutons.
