metamorphic

Banded Gneiss

Metamorphic Gneiss

AI-generated identification · may be incorrect

Hardness: 6-7 (Mohs scale), Color: light grey with dark blue/black bands, Luster: dull to pearly, Structure: foliated with distinct banding (gneissic fabric), Specific Gravity: 2.6-2.9

Identified July 14, 2026More metamorphic →

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Physical properties

Hardness: 6-7 (Mohs scale), Color: light grey with dark blue/black bands, Luster: dull to pearly, Structure: foliated with distinct banding (gneissic fabric), Specific Gravity: 2.6-2.9

Formation & geological history

Formed by high-grade regional metamorphism of pre-existing igneous or sedimentary rocks under intense heat and pressure, typically in deep crustal environments during mountain-building events.

Uses & applications

Used primarily in heavy construction, road base, as decorative garden stone, and occasionally for countertops and floor tiles when high-quality slabs are found.

Geological facts

Gneiss contains some of the oldest known rock materials on Earth, such as the Acasta Gneiss in Canada, which is over 4 billion years old.

Field identification & locations

Identified by alternating light and dark mineral layers. Commonly found in the cores of mountain ranges and eroded crystalline shields. Collectors look for sharp, high-contrast banding.