metamorphic
Quartzite Pebble
Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale); Color: ranges from white to grey, often with translucent qualities; Luster: vitreous to waxy; Crystal structure: Non-foliated, granular; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- ranges from white to grey, often with translucent qualities
- Luster
- vitreous to waxy
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Physical properties
Hardness: 7 (Mohs scale); Color: ranges from white to grey, often with translucent qualities; Luster: vitreous to waxy; Crystal structure: Non-foliated, granular; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure. The individual quartz grains recrystallize and fuse together into a dense, hard rock. Found in mountain belts globally.
Uses & applications
Used as a decorative gravel, in road construction as railroad ballast, for manufacturing glass (if high purity), and as a crushed stone for landscaping.
Geological facts
Quartzite is so hard that it can scratch glass and steel. It is often more resistant to erosion than the surrounding rock, which is why it often caps hilltops and mountain ridges. The specimen shows significant rounding, indicating it was transported by water over a long distance.
Field identification & locations
Identify in the field by its hardness (it will scratch a steel knife) and its grainy, sandpaper-like texture that resists being broken. Commonly found in riverbeds and glacial deposits throughout North America and Europe.
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