Metamorphic
Granite Gneiss
Granitic Gneiss
Hardness: 6-7 (Mohs scale), Color: Multi-colored with bands of quartz, feldspar, and darker minerals, Luster: Varies from dull to vitreous depending on the minerals, Crystal structure: Foliated, Cleavage: Imperfect to none (foliation planes), Specific gravity: 2.6 - 2.9
Identified More metamorphic →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6-7 (Mohs scale), Color: Multi-colored with bands of quartz, feldspar, and darker minerals, Luster: Varies from dull to vitreous depending on the minerals, Crystal structure: Foliated, Cleavage: Imperfect to none (foliation planes), Specific gravity: 2.6 - 2.9
Formation & geological history
Formed by high-grade regional metamorphism of igneous or sedimentary rocks. The heat and pressure cause the minerals to re-crystallize and align into bands (foliation). Age varies widely, common in Precambrian formations.
Uses & applications
Used primarily as dimension stone in construction (building facades, paving), countertops, and occasionally for landscaping.
Geological facts
Gneiss is one of the most common rock types in the Earth's lower continental crust.
Field identification & locations
Identified by its distinct banding (foliation) of light and dark minerals. Common in areas of ancient mountain building and continental shields.
More like this
