metamorphic
Quartz-veined Metamorphic Rock
Quartz-veined Schist or Gneiss
Hardness varies between 3 (for host rock) and 7 (for quartz veins) on the Mohs scale. Color is dark grey to black with contrasting white to yellowish quartz veins. Luster is vitreous on quartz veins and dull or greasy on the host rock. Structure is foliated with prominent fracture-filling hydrothermal veins.
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Physical properties
Hardness varies between 3 (for host rock) and 7 (for quartz veins) on the Mohs scale. Color is dark grey to black with contrasting white to yellowish quartz veins. Luster is vitreous on quartz veins and dull or greasy on the host rock. Structure is foliated with prominent fracture-filling hydrothermal veins.
Formation & geological history
Formed through regional metamorphism of pre-existing protoliths under high temperature and pressure, subsequently fractured and hydrothermally injected with silica-rich fluids that crystallized into quartz veins.
Uses & applications
Used primarily as decorative landscape gravel, tumbling stones, educational geological specimens, and occasionally in rough stone masonry.
Geological facts
Hydrothermal quartz veins form when hot, mineral-rich fluids travel through fractures in the Earth's crust, cooling and precipitating minerals like quartz over long geological timescales.
Field identification & locations
Easily identified by the striking visual contrast of bright quartz banding cutting through darker metamorphic host rock. Found in stream beds, glacial tills, and mountainous regions worldwide.
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