metamorphic
Quartzite Pebble
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 (Mohs scale); Color: Tan, beige, or yellowish-white; Luster: Vitreous to waxy; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 (Mohs scale)
- Color
- Tan, beige, or yellowish-white
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 (Mohs scale); Color: Tan, beige, or yellowish-white; Luster: Vitreous to waxy; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone subjected to high heat and pressure. The individual sand grains recrystallize into a silica-interlocked matrix. These pebbles are often rounded by alluvial or glacial erosional processes.
Uses & applications
Used as a construction aggregate, for landscaping, and in some industrial glass-making. Highly tumbled specimens are popular for decorative rock gardens and aquarium gravel.
Geological facts
Quartzite is so hard and chemically resistant that it often remains as pebbles long after the surrounding softer rock has eroded away. It is tougher than the sandstone from which it originated.
Field identification & locations
Identify in the field by its inability to be scratched by steel and its grainy but fused texture. Commonly found in riverbeds, glacial tills, and beaches. Collectors value it for tumbling and polishing.
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