metamorphic
Banded Gneiss Pebble
Banded Gneiss
Hardness: 6-7 on the Mohs scale. Color: Alternating dark (grey/black) and light (brownish/grey) bands. Luster: Vitreous to dull. Texture: Medium to coarse-grained metamorphic foliation. Specific Gravity: ~2.6-3.0.
- Hardness
- 6-7 on the Mohs scale
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 on the Mohs scale. Color: Alternating dark (grey/black) and light (brownish/grey) bands. Luster: Vitreous to dull. Texture: Medium to coarse-grained metamorphic foliation. Specific Gravity: ~2.6-3.0.
Formation & geological history
Formed through high-grade regional metamorphism of igneous (like granite) or sedimentary rocks under intense heat and pressure deep within Earth's crust. Rounded and smoothed by stream or beach water erosion.
Uses & applications
Used primarily for decorative rock collections, landscape design, aquariums, or as an educational geological specimen.
Geological facts
Gneiss is one of the oldest rock types on Earth, with some specimens dating back over 4 billion years (e.g., the Acasta Gneiss in Canada). The distinct banding is called gneissic banding.
Field identification & locations
Look for distinct, alternating light and dark mineral bands (foliation) in a well-rounded beach or river pebble. Commonly found in glaciated regions, riverbeds, and coastal beaches.
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