metamorphic
Quartzite Pebble
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Tan to light orange/pink; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Tan to light orange/pink
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan to light orange/pink; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone subjected to high heat and pressure, causing the original quartz grains to recrystallize into a dense interlaced structure. Typically found in mountain belts or riverbeds.
Uses & applications
Used primarily as construction aggregate, road ballast, and in landscaping. Highly rounded pebbles are often used in decorative garden paths or as aquarium gravel.
Geological facts
Quartzite is so tough that it often outlasts the mountain ranges in which it formed, frequently appearing as resistant 'caprock' on ridges or as smooth, indestructible pebbles in distant riverbeds.
Field identification & locations
Identify in the field by its inability to be scratched by a steel knife and its tendency to break across grain boundaries rather than around them. Common in glacial till and river valleys worldwide.
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