metamorphic
Quartzite Pebbles (Sugar Quartz)
Metamorphic Quartzite (SiO2)
Hardness: 7 (Mohs scale); Color: Tan, orange, or honey-brown; Luster: Dull to vitreous (sugary); Crystal Structure: Hexagonal (microcrystalline); Specific Gravity: 2.65
- Hardness
- 7 (Mohs scale)
- Color
- Tan, orange, or honey-brown
- Luster
- Dull to vitreous (sugary)
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Physical properties
Hardness: 7 (Mohs scale); Color: Tan, orange, or honey-brown; Luster: Dull to vitreous (sugary); Crystal Structure: Hexagonal (microcrystalline); Specific Gravity: 2.65
Formation & geological history
Formed when quartz-rich sandstone is subjected to heat and pressure during regional metamorphism, causing the sand grains to recrystallize into a dense interlaced structure. This specimen shows significant rounding from water erosion in a river or coastal environment.
Uses & applications
Primarily used as decorative stone, in landscaping, and sometimes as a minor source of silica in glassmaking or as an abrasive. Smooth specimens are popular for rock tumbling and pocket stones.
Geological facts
Quartzite is so durable that it can survive long-distance transport in rivers that would crush other rocks. The 'sugary' texture seen on the surface is caused by the way light reflects off the individual quartz crystal faces.
Field identification & locations
Identified by its extreme hardness (cannot be scratched by a steel knife) and its grainy, crystalline texture that resembles sugar. Commonly found in riverbeds, glacial deposits, and along beaches.
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