metamorphic
River Quartzite Siltstone
Quartz-rich Meta-siltstone (SiO2 dominated)
Hardness: 6.5-7 on Mohs scale; Color: Sage green to tan with banded concentric patterns; Luster: Dull/Waxy; Structure: Very fine-grained crystalline; Specific Gravity: 2.6-2.7.
- Hardness
- 6
- Color
- Sage green to tan with banded concentric patterns
- Luster
- Dull/Waxy
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Sage green to tan with banded concentric patterns; Luster: Dull/Waxy; Structure: Very fine-grained crystalline; Specific Gravity: 2.6-2.7.
Formation & geological history
Formed through the low-grade metamorphism and lithification of silt and sand deposits. The specimen shows significant rounded weathering (river-tumbled), likely from the Quaternary period but originating from much older Paleozoic or Mesozoic parent rock formations.
Uses & applications
Used primarily as decorative landscaping stone, aquarium gravel, or as a natural 'worry stone' for collectors due to its smooth, tumbled texture.
Geological facts
The banding seen on the small stone is likely a 'Liesegang ring' or similar sedimentary structure that was preserved during metamorphism, caused by the rhythmic precipitation of minerals within the rock pores.
Field identification & locations
Identify by its extreme hardness (will scratch glass) and smooth, rounded exterior compared to surrounding softer sedimentary rocks. Commonly found in riverbeds and glacial outwash plains. Look for the distinct concentric color bands which distinguish it from plain granite or limestone.
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