Gneiss

Hardness 6-7 on Mohs scale, grayish-pink to buff color with dark streaks, dull to earthy luster, phaneritic/foliated texture displaying compositional banding, specific gravity approximately 2.6-2.9

Formed under high-temperature and high-pressure regional metamorphism of pre-existing intrusive igneous rocks (such as granite) or sedimentary rocks deep within continental crust.

Widely used as crushed stone in construction, road base, aggregate, facing stone, and decorative landscaping rock.

Gneiss contains some of the oldest exposed rock formations on Earth, such as the Acasta Gneiss in Northwest Territories, Canada, which is over 4 billion years old.

Identified in the field by alternating light-colored (feldspar and quartz) and dark-colored (biotite and hornblende) mineral bands, known as gneissic foliation. Commonly found in shield regions and eroded mountain roots worldwide.