metamorphic
Quartzite Pebble
Quartzite (Silicon Dioxide, SiO2)
Hardness: 7 (Mohs scale); Color: Yellowish-tan to creamy white; Luster: Dull/Waxy (weathered) to Vitreous (internal); Crystal structure: Hexagonal (microcrystalline); Cleavage: None/Conchoidal fracture; Specific gravity: 2.6-2.7.
- Hardness
- 7 (Mohs scale)
- Color
- Yellowish-tan to creamy white
- Luster
- Dull/Waxy (weathered) to Vitreous (internal)
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Physical properties
Hardness: 7 (Mohs scale); Color: Yellowish-tan to creamy white; Luster: Dull/Waxy (weathered) to Vitreous (internal); Crystal structure: Hexagonal (microcrystalline); Cleavage: None/Conchoidal fracture; Specific gravity: 2.6-2.7.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone. High heat and pressure in tectonic burial environments caused the quartz grains to recrystallize and fuse together. This specimen shows signs of water-worn weathering, likely from a fluvial (river) or glacial environment.
Uses & applications
Used as an abrasive, in construction aggregate, as road ballast, and in the production of glass and industrial silica. High-purity quartzite is vital for manufacturing silicon metal.
Geological facts
Quartzite is so hard that it will scratch glass and even high-quality steel. Unlike sandstone, which breaks around the grains, quartzite is so well-fused that it breaks directly through the sand grains when fractured.
Field identification & locations
Identify in the field by its hardness (cannot be scratched by a knife) and lack of reaction to acid. It is commonly found in riverbeds, glacial tills, and mountain ranges. This smooth, rounded shape indicates long-term transport by water.
