metamorphic
Quartzite Pebble
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: typically white, tan, or light pink; Luster: vitreous (glassy) to waxy; Structure: granular, non-foliated crystalline; Cleavage: none (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- typically white, tan, or light pink
- Luster
- vitreous (glassy) to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, tan, or light pink; Luster: vitreous (glassy) to waxy; Structure: granular, non-foliated crystalline; Cleavage: none (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause the original quartz grains to recrystallize and fuse into a dense, interlocking matrix. This material often becomes rounded pebbles through fluvial or marine erosion.
Uses & applications
Commonly used in large-scale construction as railway ballast, crushed stone for roadbeds, and decorative landscaping gravel (pea gravel) due to its high durability and weather resistance.
Geological facts
Quartzite is so hard that it will scratch glass and even high-quality steel tools. Unlike sandstone, which breaks around its grains, quartzite is so well-fused that it breaks directly through the quartz grains.
Field identification & locations
Identify in the field by its hardness (cannot be scratched by a knife) and its grainy, sugary appearance on a fresh break. It is ubiquitously found in riverbeds and glacial deposits across North America and Europe.
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