metamorphic
River Stone (Quartzite/Siltstone)
Quartzite (primarily SiO2)
Hardness: 6.5-7 Mohs; Color: Brownish-tan with subtle reddish-orange undertones; Luster: Dull/Matte (water-worn); Crystal Structure: Granular/Microcrystalline; Cleavage: None; Specific Gravity: 2.6-2.7
- Hardness
- 6
- Color
- Brownish-tan with subtle reddish-orange undertones
- Luster
- Dull/Matte (water-worn)
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Physical properties
Hardness: 6.5-7 Mohs; Color: Brownish-tan with subtle reddish-orange undertones; Luster: Dull/Matte (water-worn); Crystal Structure: Granular/Microcrystalline; Cleavage: None; Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure. This specific specimen has been further shaped and smoothed over thousands of years by fluvial (river) erosion.
Uses & applications
Commonly used in landscaping, decorative ground cover, aquarium substrate, and as a natural material for stone painting or meditation (worry stones).
Geological facts
River stones are nature's tumblers; their rounded 'ellipsoid' shape is the result of constant abrasion against other rocks and sand in moving water. Quartzite is so durable that it often survives long after the surrounding softer rocks have weathered away.
Field identification & locations
Identify by its smooth, rounded surface despite being extremely hard (cannot be scratched by a steel knife). Found globally in riverbeds, beaches, and glacial deposits.
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