igneous
Coarse-grained granite or granitic gneiss
Granite; chiefly quartz, potassium feldspar, plagioclase, and biotite/hornblende. The pronounced streaking may indicate gneissic deformation.
AI-generated identification · may be incorrectHardness about 6–7 Mohs; mottled gray, white, pink, and black, with a coarse crystalline texture and generally nonmetallic vitreous-to-pearly luster. Quartz has no cleavage, feldspars show two cleavages, and density is typically 2.6–2.8 g/cm³.
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Physical properties
Hardness about 6–7 Mohs; mottled gray, white, pink, and black, with a coarse crystalline texture and generally nonmetallic vitreous-to-pearly luster. Quartz has no cleavage, feldspars show two cleavages, and density is typically 2.6–2.8 g/cm³.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in the crust, commonly during Precambrian to Phanerozoic mountain-building; gneissic banding forms when such rocks undergo intense heat and pressure.
Uses & applications
Widely used as dimension stone, countertops, monuments, aggregate, and paving; attractive polished pieces have modest decorative or collector value.
Geological facts
The image appears to show interlocking light feldspar/quartz grains among dark mafic minerals, with possible foliation rather than sedimentary layering.
Field identification & locations
Identify it by its visible interlocking crystals, lack of rounded grains or fossils, and resistance to scratching; strong planar banding favors gneiss. Common worldwide in continental shields and mountain belts.
