igneous
Pink-and-black banded granite (possibly orbicular/flow-banded granite)
Granitic rock composed chiefly of quartz, alkali feldspar, plagioclase, and biotite/hornblende
AI-generated identification · may be incorrectMedium- to coarse-grained, pink, gray, and black wavy bands; crystalline texture, vitreous to dull luster, Mohs hardness about 6–7, with no obvious cleavage as a whole. Individual feldspar crystals show cleavage; specific gravity is roughly 2.6–2.8.
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Physical properties
Medium- to coarse-grained, pink, gray, and black wavy bands; crystalline texture, vitreous to dull luster, Mohs hardness about 6–7, with no obvious cleavage as a whole. Individual feldspar crystals show cleavage; specific gravity is roughly 2.6–2.8.
Formation & geological history
An intrusive felsic igneous rock formed by slow cooling of silica-rich magma, with the banding likely produced by magmatic flow, deformation, or compositional segregation. Most granites formed in Precambrian to Phanerozoic continental crust.
Uses & applications
Used as dimension stone, countertops, paving, monuments, landscaping stone, and decorative polished material; attractive banded pieces are collected as lapidary specimens.
Geological facts
The rounded shape indicates transport and abrasion as a river cobble or glacial erratic. Pink coloration generally comes from potassium feldspar, while dark bands commonly contain biotite or amphibole.
Field identification & locations
Identify it by visible interlocking quartz and feldspar grains, abundant pink potassium feldspar, and black mica/amphibole; it is commonly found in granitic terrains and gravel deposits worldwide. A hand lens and acid test can help distinguish it from rhyolite or gneiss.
