metamorphic
Quartzite Pebble
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 on Mohs scale; Color: Grayish-tan with white quartz veins; Luster: Dull to waxy; Crystal structure: Non-foliated, granular; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Grayish-tan with white quartz veins
- Luster
- Dull to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-tan with white quartz veins; Luster: Dull to waxy; Crystal structure: Non-foliated, granular; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed when quartz-rich sandstone is subjected to high heat and pressure, causing the original quartz grains to recrystallize into a dense, interlocking mosaic of crystals. This specific specimen has been further shaped into a smooth pebble by river or beach erosion.
Uses & applications
Commonly used as crushed stone in road construction, railroad ballast, and as a decorative stone in landscaping. High-purity quartzite is used to produce silica sand for glassmaking.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, often forming the peaks of mountain ranges. It is harder than steel and will easily scratch a glass plate.
Field identification & locations
Identify in the field by its extreme hardness and its sugary, granular appearance on a fresh break. This specimen features a visible white quartz vein. They are common in riverbeds and glacial tills worldwide.
