metamorphic
Pink Granite Gneiss
Gneiss (High-grade metamorphic rock)
Hardness: 6-7 on Mohs scale; Color: Pink, orange, white, and black; Luster: Dull to vitreous; Structure: Foliated with distinct banding (gneissose banding); Gravity: 2.6-2.9
- Hardness
- 6-7 on Mohs scale
- Color
- Pink, orange, white, and black
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Pink, orange, white, and black; Luster: Dull to vitreous; Structure: Foliated with distinct banding (gneissose banding); Gravity: 2.6-2.9
Formation & geological history
Formed from the high-pressure and high-temperature metamorphism of granite or sedimentary protoliths. This process typically occurs deep within the Earth's crust during mountain-building events (orogenies) over millions of years.
Uses & applications
Used as a decorative building stone, for countertops, floor tiles, and as crushed stone for road construction and railroad ballast. Exceptionally durable for outdoor monuments.
Geological facts
Gneiss is one of the oldest known rock types on Earth; the Acasta Gneiss in Canada is approximately 4.03 billion years old. The term 'gneiss' comes from a Middle High German verb meaning 'to spark'.
Field identification & locations
Identified by its alternating layers of light-colored minerals (quartz and feldspar) and dark-colored minerals (biotite or hornblende). Common in continental shields and mountain cores. Field identification involves looking for the visible alignment of mineral grains.
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