metamorphic
River Stone (Quartzite Pebble)
Metamorphosed Quartz-rich Sandstone (SiO2)
Hardness: 7 on Mohs scale; Color: Brownish, tan, or grey; Luster: Dull to waxy when unpolished; Crystal structure: Non-foliated granoblastic; Cleavage: None; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Brownish, tan, or grey
- Luster
- Dull to waxy when unpolished
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Physical properties
Hardness: 7 on Mohs scale; Color: Brownish, tan, or grey; Luster: Dull to waxy when unpolished; Crystal structure: Non-foliated granoblastic; Cleavage: None; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure, then rounded by fluvial (river) erosion over thousands of years.
Uses & applications
Used primarily in landscaping, construction aggregates, decorative gravel, and occasionally as tumbling rough for lapidary hobbies.
Geological facts
Quartzite is so durable that it often survives intense weathering that destroys other rocks. It is commonly found in riverbeds far from its original source.
Field identification & locations
Identify by its hardness (will scratch glass) and lack of reaction to acid. Look for smooth, rounded edges and a microcrystalline sugary texture on fresh breaks.
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