metamorphic
Quartzite pebble
Metamorphic Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale); Color: Tan, brownish-pink, translucent; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- Tan, brownish-pink, translucent
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Tan, brownish-pink, translucent; 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 sandstone under high heat and pressure, typically during mountain-building events (orogeny). This specific specimen appears water-worn and rounded by fluvial or alluvial activity.
Uses & applications
Used as aggregate in construction, railway ballast, and occasionally as decorative landscaping stone. High-purity quartzite is used to produce silica sand for glassmaking.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock layers, forming prominent ridges and peaks in mountainous terrain. It is often harder than the steel blade of a knife.
Field identification & locations
Identify in the field by its inability to be scratched by steel and its granular, sugary texture on fresh breaks. It is ubiquitous in riverbeds and glacial till throughout North America and Europe.
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