Gneiss

Hardness of 6-7 on the Mohs scale, characterized by distinctive alternating light and dark mineral bands (gneissic banding), vitreous to dull luster, granular to foliated crystal structure, specific gravity around 2.6-2.9.

Formed by high-temperature and high-pressure metamorphic processes acting on pre-existing igneous or sedimentary rocks (such as granite or schist) deep within the Earth's crust, typically during mountain-building events over millions of years.

Used primarily in construction as crushed stone for road aggregates, building facings, flooring, and dimensional stone.

Gneiss contains some of the oldest rocks found on Earth, with certain gneiss formations dating back over 4 billion years.

Easily identified in the field by its striking zebra-like light and dark compositional banding. Commonly found in ancient shield areas and core of major mountain ranges.