metamorphic
Gneiss (with Quartz Vein / Pegmatite Banding)
Metamorphic Gneiss
Hardness: 6-7 on Mohs scale. Color: Mottled grey, white, and dark green/black. Luster: Vitreous to dull. Texture: Coarse-grained foliated metamorphic rock showing distinct light quartz/feldspar bands and dark amphibole/biotite matrix.
- Hardness
- 6-7 on Mohs scale
- Color
- Mottled grey, white, and dark green/black
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Mottled grey, white, and dark green/black. Luster: Vitreous to dull. Texture: Coarse-grained foliated metamorphic rock showing distinct light quartz/feldspar bands and dark amphibole/biotite matrix.
Formation & geological history
Formed under intense regional metamorphism at high pressures and high temperatures deep within the Earth's crust, causing segregation of mineral phases into distinct banding.
Uses & applications
Used as crushed stone in road construction, dimensional stone in building facades, landscape rock, and decorative garden specimens.
Geological facts
Gneiss is one of the oldest rock types on Earth; the Acasta Gneiss in Canada is approximately 4 billion years old.
Field identification & locations
Identified in the field by alternating light quartz/feldspar veins and dark mineral banding. Commonly found in glaciated riverbeds, mountainous regions, and shield areas worldwide.
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