Gneiss

Typically contains quartz, feldspar, and dark biotite or hornblende in coarse, alternating bands; hardness about 6–7 Mohs, nonmetallic vitreous-to-pearly luster, granular crystalline texture, and poor cleavage as a whole. The specimen shows light gray-white bands with black, shiny mafic minerals and possible rusty weathering.

Formed by intense regional metamorphism of granite or sedimentary protoliths at high temperature and pressure, commonly during Precambrian to Paleozoic mountain-building events. Exact age cannot be determined from the photograph.

Used as dimension stone, architectural facing, landscaping aggregate, and monuments; attractive polished pieces are collected but usually have modest commercial value.

Gneissic banding results from segregation and alignment of minerals during deformation; it is distinguished from granite by compositional layering or foliation rather than uniform texture.

Identify it by coarse grains and alternating light quartz-feldspar layers with dark mica/amphibole bands; common in ancient continental shields and metamorphic mountain belts worldwide. A fresh surface, streak, magnetism, and hardness tests can refine identification.