metamorphic
Gneiss Pebble
Gneiss (Metamorphic Foliated Rock)
Hardness around 6-7 on Mohs scale; light pinkish-tan and white quartz/feldspar background with distinct dark green/black biotite or amphibole bands (gneissic banding); dull to sub-vitreous luster; coarse-grained texture; rounded water-worn pebble morphology.
Identified More metamorphic →
Explore Gneiss Pebble in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness around 6-7 on Mohs scale; light pinkish-tan and white quartz/feldspar background with distinct dark green/black biotite or amphibole bands (gneissic banding); dull to sub-vitreous luster; coarse-grained texture; rounded water-worn pebble morphology.
Formation & geological history
Formed through high-grade regional metamorphism of pre-existing igneous rocks (like granite) or sedimentary rocks under high temperature and pressure deep within the Earth's crust, causing light and dark minerals to separate into distinct parallel bands.
Uses & applications
Crushed stone for construction aggregate, decorative landscaping river rock, dimension stone, and educational geological specimens.
Geological facts
Gneiss is one of the oldest rock types on Earth, with some specimens like the Acasta Gneiss in Canada dating back over 4 billion years.
Field identification & locations
Identified in the field by its distinct alternating dark and light parallel mineral bands (gneissic foliation) that do not split easily along planes like schist. Commonly found in glaciated riverbeds, beaches, and ancient metamorphic shield terrains.
More like this
