metamorphic
Quartzite Pebble
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Off-white, yellowish, or tan; Luster: Vitreous to waxy; Structure: Granoblastic (interlocking quartz grains); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- Off-white, yellowish, or tan
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Off-white, yellowish, or tan; Luster: Vitreous to waxy; Structure: Granoblastic (interlocking quartz grains); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7.
Formation & geological history
Formed from the metamorphism of quartz sandstone under intense heat and pressure, typically in convergent plate boundaries. The specimen shown is a water-worn river pebble, likely shaped over thousands of years by fluvial erosion.
Uses & applications
Used as a decorative landscape stone, in road construction (as crushed stone), in the manufacture of glass and ceramics, and as a component in decorative masonry.
Geological facts
Quartzite is so durable that it can survive long-distance transport in rivers and high-energy beach environments where other rocks would crumble. It is harder than steel and can easily scratch glass.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by a steel knife) and its sugary, granular texture hidden beneath the smooth, water-worn surface. Commonly found in riverbeds, glacial till, and mountainous regions.
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