igneous
Pegmatitic granite
Granite, a coarse-grained quartz–feldspar rock with accessory mica and iron-oxide staining
AI-generated identification · may be incorrectVisible interlocking white/pink feldspar, translucent gray quartz, and dark brown-black mica or weathered iron oxides; Mohs hardness about 6–7, vitreous to dull luster, no preferred cleavage as a rock, and granular texture. The rusty brown patches likely represent oxidation or biotite alteration.
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Physical properties
Visible interlocking white/pink feldspar, translucent gray quartz, and dark brown-black mica or weathered iron oxides; Mohs hardness about 6–7, vitreous to dull luster, no preferred cleavage as a rock, and granular texture. The rusty brown patches likely represent oxidation or biotite alteration.
Formation & geological history
Formed when silica-rich magma cooled slowly deep within the crust, allowing large crystals to grow; pegmatitic varieties crystallized from late-stage, volatile-rich melt. Typically Precambrian to Phanerozoic, depending on its intrusion.
Uses & applications
Used as dimension stone, countertops, aggregate, monuments, and landscaping rock; attractive pieces are collected, though this fragment has limited gem value.
Geological facts
Quartz is usually gray and glassy, feldspar is commonly white or pink, and mica occurs as dark platy flakes. Large crystals and rare minerals can occur in true pegmatites.
Field identification & locations
Identify by its coarse interlocking crystals and inability to scratch quartz; it commonly occurs in continental batholiths and granitic veins worldwide. A fresh surface and hand lens would improve identification.
