metamorphic
Banded Gneiss
Gneiss (SiO2 enriched metamorphic rock)
Hardness: 6-7 on Mohs scale. Color: Alternating dark (biotite/amphibole) and light (quartz/feldspar) bands. Luster: Vitreous to dull. Crystal structure: Medium to coarse-grained foliated texture. Cleavage: Poor, splits along irregular plane surfaces.
- Hardness
- 6-7 on Mohs scale
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Alternating dark (biotite/amphibole) and light (quartz/feldspar) bands. Luster: Vitreous to dull. Crystal structure: Medium to coarse-grained foliated texture. Cleavage: Poor, splits along irregular plane surfaces.
Formation & geological history
Formed by high-grade regional metamorphism of igneous rocks like granite or sedimentary rocks like shale under intense heat and pressure deep within Earth's crust.
Uses & applications
Used as a crushed stone in construction, road building, and as an attractive landscaping stone or decorative rock in aquariums and gardens.
Geological facts
The alternating light and dark bands are created by mineral segregation during intense metamorphic forces, a process known as gneissic banding.
Field identification & locations
Identified in the field by its distinctive parallel, alternating light-and-dark mineral stripes. It is widely distributed in continental shield areas and mountainous terrains.
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