metamorphic
Quartzite Pebbler
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Off-white to light gray with slight tan undertones; Luster: Vitreous to dull/earthy when weathered; Crystal Structure: Granular/crystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6 - 2.7
- Hardness
- 7 on Mohs scale
- Color
- Off-white to light gray with slight tan undertones
- Luster
- Vitreous to dull/earthy when weathered
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Physical properties
Hardness: 7 on Mohs scale; Color: Off-white to light gray with slight tan undertones; Luster: Vitreous to dull/earthy when weathered; Crystal Structure: Granular/crystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6 - 2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under intense heat and pressure, typically during mountain-building events. The specimen shown is a water-worn river cobble or 'pebble' that has been smoothed by fluvial or coastal erosion.
Uses & applications
Used in construction as crushed stone or railway ballast, in the glass industry as a source of silica, and as decorative landscaping stones. Highly polished versions are used for aquarium gravel.
Geological facts
Quartzite is so durable that it can survive long periods of erosion, which is why it is often found as smooth pebbles in riverbeds far from its original source. It is harder than steel and can scratch glass easily.
Field identification & locations
Identify in the field by its sugary, granular texture and its inability to be scratched by a steel knife. It is commonly found in gravel pits, riverbeds, and ancient beaches. Collectors often look for examples with unique shapes or translucency.
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