metamorphic
River Stone (Quartzite)
Metamorphic Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Tan, beige, or grey with subtle banding; Luster: Dull to vitreous; Crystal structure: Non-foliated granoblastic; Cleavage: None (conchoidal fracture)
- Hardness
- 7 on Mohs scale
- Color
- Tan, beige, or grey with subtle banding
- Luster
- Dull to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, beige, or grey with subtle banding; Luster: Dull to vitreous; Crystal structure: Non-foliated granoblastic; Cleavage: None (conchoidal fracture)
Formation & geological history
Formed from the metamorphism of quartz sandstone under high heat and pressure. It has been subsequentally weathered and rounded by fluvial action (moving water) over thousands of years.
Uses & applications
Landscaping, decorative garden paths, architectural stone, and as an abrasive in industrial applications. Smaller, smooth specimens are popular for rock painting and stress-relief stones.
Geological facts
Quartzite is so hard that it will scratch glass and even high-quality steel. This specific specimen is a 'clast' that has traveled through water, giving it its distinctive ellipsoidal shape.
Field identification & locations
Identified by its extreme hardness, lack of reactivity to acid, and smooth, water-worn exterior. Found globally in riverbeds, glacial deposits, and beaches. Look for its sugary texture under a magnifying lens.
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