igneous
Pink-and-green granite or granitic gneiss
Coarse-grained granitoid, chiefly quartz, feldspar, and dark mafic minerals; pink areas likely potassium feldspar
AI-generated identification · may be incorrectHardness about 6–7 Mohs; mottled pink, gray, black, and green with a granular texture and mostly vitreous to dull luster. Interlocking crystals show no obvious cleavage as a whole, though feldspar has cleavage; specific gravity commonly 2.6–2.8.
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Physical properties
Hardness about 6–7 Mohs; mottled pink, gray, black, and green with a granular texture and mostly vitreous to dull luster. Interlocking crystals show no obvious cleavage as a whole, though feldspar has cleavage; specific gravity commonly 2.6–2.8.
Formation & geological history
Formed by slow cooling of silica-rich magma deep in the crust, likely during Precambrian to Paleozoic continental plutonism; strong foliation, if present, could indicate later metamorphism into gneiss.
Uses & applications
Used as crushed stone, aggregate, dimension stone, monuments, countertops, and landscaping rock; attractive polished pieces may be collectible but are generally inexpensive.
Geological facts
The pink coloration commonly comes from potassium feldspar, while green-black grains may be biotite, amphibole, or altered chlorite. A true gneiss will show compositional banding or mineral alignment rather than a uniformly random granite texture.
Field identification & locations
Identify it by visible interlocking quartz and feldspar crystals, abundant pink feldspar, and dark mafic grains; streak and acid tests are usually unhelpful. Common in continental shields, mountain belts, and granite quarries worldwide.
