Gneiss

Hardness of 6-7 on Mohs scale; pink, gray, black, and white banded color; vitreous luster; foliated texture with distinct alternating light and dark mineral bands (gneissic banding); specific gravity around 2.6-2.9.

Formed by high-grade regional metamorphism, where preexisting rocks such as granite or sedimentary rocks are subjected to extreme heat and directed pressure deep within the Earth's crust.

Commonly used in construction, as crushed stone for road base, building facades, and occasionally as dimension stone for countertops and architectural tiles.

Gneiss includes some of the oldest rocks found on Earth, with certain specimens dating back over 4 billion years, such as the Acasta Gneiss in Canada.

Easily identified in the field by its characteristic alternating bands of light-colored minerals (like quartz and feldspar) and dark-colored minerals (like biotite and hornblende). Found worldwide in ancient shield areas and mountain belts.