igneous
Weathered granite or granitic gneiss
Granite; primarily quartz (SiO₂), feldspar, and mica, with iron-oxide staining
AI-generated identification · may be incorrectCoarse-grained, mottled white, gray, pink, and reddish-brown; vitreous quartz and dull feldspar, with possible mica. Hardness about 6–7 Mohs, no prominent cleavage as a whole, and specific gravity roughly 2.6–2.7.
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Physical properties
Coarse-grained, mottled white, gray, pink, and reddish-brown; vitreous quartz and dull feldspar, with possible mica. Hardness about 6–7 Mohs, no prominent cleavage as a whole, and specific gravity roughly 2.6–2.7.
Formation & geological history
Formed when silica-rich magma cooled slowly deep underground, allowing visible crystals to grow; likely Precambrian to younger, then exposed and weathered at the surface. The reddish coloration is probably oxidation of iron-bearing minerals.
Uses & applications
Commonly used as building stone, countertops, monuments, aggregate, and landscaping rock; attractive pieces may be polished as decorative specimens. This irregular weathered sample has modest jewelry or lapidary value.
Geological facts
Granite’s visible interlocking crystals distinguish it from fine-grained volcanic rocks such as rhyolite. If faint banding or flattened mineral alignment is present, the specimen may instead be granitic gneiss.
Field identification & locations
Common worldwide, especially in continental mountain belts and exposed shields; notable sources include India, Brazil, Scandinavia, and North America. Confirm with a hand lens, glass-scratch test, and streak/acid tests; exact identification requires microscopy or thin-section analysis.
