metamorphic
Gneiss with Quartz Vein
Gneiss containing Quartz (SiO2) filler
Hardness: 6-7 (Mohs scale); Color: Banded gray, black, and white; Luster: Vitreous on quartz, dull to pearly on gneiss; Structure: Foliated with crystalline vein; Cleavage: None (conchoidal fracture in quartz).
- Hardness
- 6-7 (Mohs scale)
- Color
- Banded gray, black, and white
- Luster
- Vitreous on quartz, dull to pearly on gneiss
Identified More metamorphic →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6-7 (Mohs scale); Color: Banded gray, black, and white; Luster: Vitreous on quartz, dull to pearly on gneiss; Structure: Foliated with crystalline vein; Cleavage: None (conchoidal fracture in quartz).
Formation & geological history
Formed through high-grade regional metamorphism of igneous or sedimentary protoliths. The quartz vein formed via hydrothermal fluids filling fractures during tectonic activity.
Uses & applications
Used primarily as crushed stone for road construction, railroad ballast, and occasionally as decorative building stone or 'landscaping rock'.
Geological facts
Gneiss is one of the oldest rock types on Earth, with some specimens in the Acasta Gneiss complex dating back over 4 billion years. The banding is caused by the segregation of minerals under intense pressure.
Field identification & locations
Identify by looking for 'Gneissic banding' (alternating dark and light layers). In the field, look for cross-cutting veins where minerals filled cracks in the host rock. Extremely common in shield areas like Canada or Scandinavia.
More like this
