metamorphic
Quartzite Pebble
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 on Mohs scale; Color: Tan to off-white; Luster: Dull to slightly vitreous; Texture: Granular but smooth due to river wear; Cleavage: None
- Hardness
- 7 on Mohs scale
- Color
- Tan to off-white
- Luster
- Dull to slightly vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan to off-white; Luster: Dull to slightly vitreous; Texture: Granular but smooth due to river wear; Cleavage: None
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure fused individual sand grains into a solid crystalline rock. Geological age varies but commonly Precambrian to Paleozoic.
Uses & applications
Used primarily in construction as crushed stone or road ballast. High-quality quartzite is used as dimension stone in architecture. Small pebbles are often used in landscaping or as tumbling media.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock during erosion, forming resistant ridges or caprocks in mountainous terrain. It is frequently mistaken for quartz mineral, but has a characteristic 'sugary' texture.
Field identification & locations
Identify in the field by its inability to be scratched by a steel knife and its lack of reaction to acid. Commonly found in riverbeds, glacial tills, and ancient mountain belts. Look for a grainy surface that breaks across the grains rather than around them.
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