igneous
Weathered feldspathic granite (probable)
Granite; primarily quartz (SiO₂), feldspar, and mica/amphibole
AI-generated identification · may be incorrectCoarse, uneven crystalline texture with pale pink/tan feldspar, whitish quartz, and dark mineral flecks; typically Mohs 6–7, vitreous-to-dull luster, no consistent cleavage as a whole, and specific gravity about 2.6–2.7. Strong surface weathering makes the grain boundaries and colors indistinct.
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Physical properties
Coarse, uneven crystalline texture with pale pink/tan feldspar, whitish quartz, and dark mineral flecks; typically Mohs 6–7, vitreous-to-dull luster, no consistent cleavage as a whole, and specific gravity about 2.6–2.7. Strong surface weathering makes the grain boundaries and colors indistinct.
Formation & geological history
Likely intrusive igneous rock crystallized slowly from silica-rich magma deep underground, commonly during Precambrian to younger continental crust formation; later uplift and chemical weathering produced the rounded, rusty surface.
Uses & applications
Used widely as crushed aggregate, road stone, building stone, monuments, countertops, and landscaping material; this weathered hand specimen has little commercial value.
Geological facts
The brown coloration commonly results from oxidation of iron-bearing biotite or amphibole and staining by iron oxides. The photograph is insufficient to distinguish granite confidently from weathered granodiorite or gneiss.
Field identification & locations
Look for interlocking visible quartz and feldspar grains, unlike sandstone’s cemented grains; acid testing, a fresh broken surface, and a hand lens would improve identification. Common worldwide in continental shields and large intrusive batholiths.
