metamorphic
Banded gneiss (likely amphibolite-bearing gneiss)
Gneiss; quartz–feldspar–mica/amphibole aggregate
AI-generated identification · may be incorrectHardness about 6–7 Mohs; dark gray-green and cream bands, granular texture, and dull to subtly vitreous luster. The light veins are likely quartz or feldspar; foliation is visible but the specimen is rounded and water-worn.
Identified More metamorphic →
Explore Banded gneiss (likely amphibolite-bearing gneiss) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness about 6–7 Mohs; dark gray-green and cream bands, granular texture, and dull to subtly vitreous luster. The light veins are likely quartz or feldspar; foliation is visible but the specimen is rounded and water-worn.
Formation & geological history
Formed when pre-existing igneous or sedimentary rock underwent high-grade metamorphism, typically at roughly 600–800°C during mountain building. Gneiss commonly records Precambrian to Paleozoic metamorphic events.
Uses & applications
Used locally as crushed stone, aggregate, landscaping rock, and occasionally decorative dimension stone; attractive pieces are collected but are not generally gemstone-grade.
Geological facts
Alternating mineral bands reflect segregation during intense metamorphism, not ordinary sedimentary layering. Dark portions may contain biotite, hornblende, or other ferromagnesian minerals.
Field identification & locations
Identify it by strong light–dark banding, interlocking grains, lack of bubbles, and resistance to scratching by a steel knife. Common in exposed mountain belts and glacial or stream gravels; exact identification would require a fresh surface or thin section.
More like this
