igneous
Weathered granite (likely granitic pegmatite)
Coarse-grained granite; chiefly quartz (SiO₂), feldspar, and mica
AI-generated identification · may be incorrectHardness about 6–7 overall; mottled white, gray, tan, and black with a granular texture and vitreous to pearly mineral luster. Visible interlocking crystals suggest quartz and feldspar with dark biotite or hornblende; cleavage occurs in feldspar and mica, not quartz.
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Physical properties
Hardness about 6–7 overall; mottled white, gray, tan, and black with a granular texture and vitreous to pearly mineral luster. Visible interlocking crystals suggest quartz and feldspar with dark biotite or hornblende; cleavage occurs in feldspar and mica, not quartz.
Formation & geological history
A plutonic igneous rock crystallized slowly from silica-rich magma deep in Earth’s crust, probably millions to billions of years ago; its rough surface reflects weathering and erosion.
Uses & applications
Used as crushed aggregate, building stone, countertops, monuments, and landscaping material; attractive coarse crystals may have modest collecting value.
Geological facts
Granite’s large crystals form because underground magma cools slowly. The specimen may be pegmatitic if some crystals are unusually large, but the image alone cannot confirm that distinction.
Field identification & locations
Identify it by its coarse interlocking grains, pale feldspar/quartz, and scattered dark mica; it commonly occurs in continental mountain belts and exposed plutons worldwide. A hand lens and streak, hardness, or acid tests can refine identification.
