Gneissic River Pebble

Mohs hardness 6-7, color ranges from gray to brown with light and dark banding (foliation), dull to pearly luster, coarse-grained texture, no distinct cleavage.

Formed through high-grade regional metamorphism of pre-existing igneous or sedimentary rocks under extreme pressure and temperature. This specific specimen has been further shaped and smoothed by river erosion (fluvial action).

Primarily used as crushed stone for construction, road basework, and landscaping. Polished varieties are used in countertops and ornamental building stone.

Gneiss is one of the oldest known rock types on Earth; the Acasta Gneiss in Canada is approximately 4 billion years old. The distinctive banding is called 'gneissic banding' and results from the segregation of different mineral types.

Identify in the field by looking for distinct layers or bands of color in a very hard, dense rock, often found in riverbeds or glacial deposits. Common in mountainous regions or ancient continental shields.