metamorphic
Banded Gneiss
Gneiss (Metamorphic rock)
Hardness of 6-7 on the Mohs scale, characterized by distinctive alternating light and dark compositional banding (gneissic banding), vitreous to dull luster, granular to crystalline texture, no distinct cleavage.
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Physical properties
Hardness of 6-7 on the Mohs scale, characterized by distinctive alternating light and dark compositional banding (gneissic banding), vitreous to dull luster, granular to crystalline texture, no distinct cleavage.
Formation & geological history
Formed through high-grade regional metamorphism, where pre-existing igneous or sedimentary rocks (such as granite or shale) are subjected to extreme heat and directed pressure deep within the Earth's crust, typically during mountain-building events.
Uses & applications
Used primarily as dimension stone, building material, gravel, and crushed stone for road construction, as well as decorative landscaping and countertops.
Geological facts
Gneiss contains some of the oldest rocks found on Earth, dating back over 4 billion years in certain cratons like the Acasta Gneiss in Canada.
Field identification & locations
Easily identified in the field by its striking zebra-like light and dark bands consisting of minerals like quartz, feldspar, biotite, and hornblende; found worldwide in ancient shield areas and core of major mountain ranges.
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