metamorphic
Banded Gneiss
Gneiss
Hardness: 6-7 on Mohs scale; Color: Alternating light and dark bands (pinkish-white and grey/black); Luster: Vitreous to dull; Crystal structure: Foliated, granular texture with distinct mineral banding; Specific gravity: 2.6-2.9
- Hardness
- 6-7 on Mohs scale
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Alternating light and dark bands (pinkish-white and grey/black); Luster: Vitreous to dull; Crystal structure: Foliated, granular texture with distinct mineral banding; Specific gravity: 2.6-2.9
Formation & geological history
Formed through high-grade regional metamorphism of preexisting igneous or sedimentary rocks (such as granite or shale) deep within the Earth's crust under intense heat and directed pressure.
Uses & applications
Commonly used as crushed stone for road construction, building foundations, and architectural dimension stone for facing and paving.
Geological facts
Gneiss contains some of the oldest known rock material on Earth, with certain zircon grains within gneiss formations dating back over 4 billion years.
Field identification & locations
Easily identified in the field by its distinct alternating light and dark compositional banding known as gneissic banding. Found globally in ancient shields and core mountain ranges.
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