metamorphic
Gneiss with Quartz Veining
Gneiss (High-grade Regional Metamorphic Rock)
Features distinct foliation or 'gneissic banding', hardness of 6-7 on Mohs scale, colors ranging from grey and white to tan/rusty brown due to oxidation. Displays granular texture and contains crystalline quartz inclusions.
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Physical properties
Features distinct foliation or 'gneissic banding', hardness of 6-7 on Mohs scale, colors ranging from grey and white to tan/rusty brown due to oxidation. Displays granular texture and contains crystalline quartz inclusions.
Formation & geological history
Formed through high-pressure, high-temperature regional metamorphism of igneous or sedimentary protoliths, often deep within the Earth's crust during mountain-building events (orogeny).
Uses & applications
Primarily used as a crushed stone for construction, road base, or as dimension stone for counter tops and landscaping. Used by collectors to study structural geology.
Geological facts
Gneiss can be among the oldest rocks on Earth; the Acasta Gneiss in Canada is approximately 4 billion years old. The quartz veins seen here likely formed later as silica-rich fluids filled fractures in the metamorphic rock.
Field identification & locations
Identify by looking for alternating layers of different minerals (foliation) and lack of cleavage (unlike schist). Commonly found in the crystalline cores of mountain ranges and glacial till.
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