metamorphic
Banded Gneiss with Quartz Vein
Gneiss containing SiO2 (Quartz) intrusion
Hardness: 6.5-7 (Mohs); Color: Dark grey/blue host rock with a white/cream band; Luster: Dull/earthy host with vitreous vein; Structure: Foliated with visible banding and a hydrothermal mineral vein.
- Hardness
- 6
- Color
- Dark grey/blue host rock with a white/cream band
- Luster
- Dull/earthy host with vitreous vein
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Dark grey/blue host rock with a white/cream band; Luster: Dull/earthy host with vitreous vein; Structure: Foliated with visible banding and a hydrothermal mineral vein.
Formation & geological history
Formed through high-grade regional metamorphism of igneous or sedimentary protoliths under extreme heat and pressure. The white band is a hydrothermal vein formed when mineral-rich water filled a crack in the rock and crystallized as quartz or calcite.
Uses & applications
Primarily used as crushed stone for road construction or as decorative river rocks; certain types are used as dimensional stone for counter-tops.
Geological facts
The white line is often called a 'wishing stone.' Folklore suggests that if you find a rock with a continuous white line encircling it, you can make a wish upon it.
Field identification & locations
Identify in the field by the distinct light-colored mineral vein cutting through a darker, often foliated or crystalline matrix. Found frequently in glacial till and riverbeds in mountainous regions.
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