metamorphic
Likely weathered gneiss
Foliated metamorphic rock, commonly quartz–feldspar–mica gneiss
AI-generated identification · may be incorrectCoarse, irregularly banded gray-and-white rock with dark mica-rich areas; quartz and feldspar give a vitreous to dull luster. Hardness is approximately 6–7 Mohs; no obvious cleavage as a whole rock, though mica may split into sheets.
Identified More metamorphic →
Explore Likely weathered gneiss in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Coarse, irregularly banded gray-and-white rock with dark mica-rich areas; quartz and feldspar give a vitreous to dull luster. Hardness is approximately 6–7 Mohs; no obvious cleavage as a whole rock, though mica may split into sheets.
Formation & geological history
Formed when granite or other felsic rock underwent intense regional metamorphism, recrystallizing and segregating minerals into bands, typically during Precambrian to younger mountain-building events.
Uses & applications
Used as crushed aggregate, building stone, decorative slabs, and landscape rock; this small rough specimen has mainly educational or collecting value.
Geological facts
The apparent light and dark streaks are mineral segregation rather than sedimentary layering. Strong foliation and coarse grains distinguish gneiss from unfoliated granite.
Field identification & locations
Look for alternating quartz–feldspar-rich and biotite/hornblende-rich bands, visible interlocking grains, and a hard, durable texture. Common worldwide in ancient continental shields and metamorphic mountain belts; exact identification would benefit from a fresh surface or thin section.
More like this
