igneous
Granite (likely orbicular/graphic pegmatitic granite)
Coarse-grained granitoid composed mainly of quartz, feldspar, and biotite/hornblende
AI-generated identification · may be incorrectHardness about 6–7 Mohs; pale cream to gray with black mica or amphibole and scattered pinkish feldspar. Coarse interlocking crystals, vitreous quartz luster, and no obvious cleavage as a whole; specific gravity about 2.6–2.8.
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Physical properties
Hardness about 6–7 Mohs; pale cream to gray with black mica or amphibole and scattered pinkish feldspar. Coarse interlocking crystals, vitreous quartz luster, and no obvious cleavage as a whole; specific gravity about 2.6–2.8.
Formation & geological history
A plutonic igneous rock formed by slow crystallization of silica-rich magma deep underground, commonly during Precambrian to Phanerozoic mountain-building events. The rounded shape appears tumbled or naturally weathered.
Uses & applications
Used as dimension stone, countertops, monuments, aggregate, and polished decorative stone; attractive pieces are sold as lapidary specimens. Typical value is about $5–$30 for a palm-sized common specimen, or $30–$100+ if unusually patterned and polished.
Geological facts
Its visible crystals indicate slow cooling, while the dark minerals are commonly biotite or hornblende. Feldspar-rich varieties may be marketed as decorative granite or pegmatitic granite.
Field identification & locations
Identify it by coarse interlocking light feldspar/quartz and dark mica or amphibole, unlike basalt’s fine grain. Common worldwide in continental crust and granite plutons, including India, Brazil, Scandinavia, Canada, and the United States.
