metamorphic
Gneiss Pebble
Orthogneiss / Paragneiss
AI-generated identification · may be incorrectHardness 6-7 on Mohs scale; mottled gray, black, and white coloration; vitreous to dull luster; foliated texture with distinct mineral banding.
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Physical properties
Hardness 6-7 on Mohs scale; mottled gray, black, and white coloration; vitreous to dull luster; foliated texture with distinct mineral banding.
Formation & geological history
Formed through high-temperature and high-pressure regional metamorphism of pre-existing igneous or sedimentary rocks deep within the Earth's crust.
Uses & applications
Used primarily as crushed stone for construction, road base, and decorative landscaping or architectural facing stone.
Geological facts
Gneiss contains some of the oldest known minerals on Earth, surviving billions of years of tectonic recycling.
Field identification & locations
Easily identified by its characteristic alternating dark and light mineral bands (gneissic banding). Commonly found weathered into smooth pebbles along beaches and riverbeds.
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