metamorphic
Gneiss
Gneiss
Hardness of 6-7 on the Mohs scale; displays distinct alternating light and dark bands (gneissic banding) composed of quartz, feldspar, mica, and amphibole; vitreous to dull luster.
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Physical properties
Hardness of 6-7 on the Mohs scale; displays distinct alternating light and dark bands (gneissic banding) composed of quartz, feldspar, mica, and amphibole; vitreous to dull luster.
Formation & geological history
Formed by high-grade regional metamorphism, typically originating from igneous rocks like granite or sedimentary rocks like shale subjected to extreme heat and pressure deep within the Earth's crust.
Uses & applications
Used primarily as dimension stone in construction, building facades, paving, and occasionally as decorative landscaping rock or crushed stone for road bases.
Geological facts
Gneiss contains some of the oldest rocks found on Earth, with certain formations dating back over 4 billion years.
Field identification & locations
Easily identified by its characteristic zebra-like banding of light and dark minerals; commonly found in ancient shield areas and deeply eroded mountain belts.
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