metamorphic
River Rock (Gneiss/Schist mix)
Foliated Metamorphic Rock (Gneiss)
Hardness: 6-7 on Mohs scale; Color: Gray, tan, and white with dark flecks; Luster: Dull to slightly vitreous; Crystal structure: Coarse-grained with visible banding (foliation); Cleavage: Poor; Specific gravity: 2.6-2.9
- Hardness
- 6-7 on Mohs scale
- Color
- Gray, tan, and white with dark flecks
- Luster
- Dull to slightly vitreous
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Gray, tan, and white with dark flecks; Luster: Dull to slightly vitreous; Crystal structure: Coarse-grained with visible banding (foliation); Cleavage: Poor; Specific gravity: 2.6-2.9
Formation & geological history
Formed through high-grade regional metamorphism of pre-existing igneous or sedimentary rocks under intense heat and pressure deep within the Earth's crust, often during mountain-building events (orogenies).
Uses & applications
Commonly used as decorative landscaping stone, in construction as crushed stone for road bases, and sometimes as architectural stone. Smooth river-worn specimens are popular for meditation and home decor.
Geological facts
This specimen is a 'river rock,' meaning its rounded shape was created by years of water erosion and tumbling in a stream or river bed. The banding indicates it was once part of a larger metamorphic formation.
Field identification & locations
Identify by looking for distinct layers or bands of different colored minerals (foliation) and a smooth, water-worn texture. Commonly found in riverbeds, glacial deposits, and mountainous regions.
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