Banded Gneiss

Hardness: 6-7 (Mohs scale), Color: Alternating bands of light and dark grey or white, Luster: Vitreous to dull, Crystal Structure: Foliated (Gneissose banding), Cleavage: Poor, Specific Gravity: 2.6-2.9

Formed through high-grade regional metamorphism of pre-existing igneous or sedimentary rocks (protoliths) under extreme pressure and temperature. This process aligns minerals into distinct bands. Common ages range from Precambrian to Cenozoic.

Used primarily in construction for crushed stone, road base, and dimension stone for countertops, flooring, and gravestones. Tumbled specimens are used for educational kits or as decorative gravel.

Gneiss contains the oldest rock found on Earth, the Acasta Gneiss in Canada, which is approximately 4.03 billion years old. The term 'gneiss' comes from an old German verb 'gneist' meaning to spark.

Identify by looking for distinct parallel banding (foliation) where minerals are segregated into dark and light layers. It is found globally in mountain ranges and ancient continental shields. Collectors should look for unique mineral inclusions like garnet.