metamorphic
Quartzite Pebble
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Tan to pale orange-brown; Luster: Vitreous to dull (when weathered); Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.63–2.65
- Hardness
- 7 on Mohs scale
- Color
- Tan to pale orange-brown
- Luster
- Vitreous to dull (when weathered)
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan to pale orange-brown; Luster: Vitreous to dull (when weathered); Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.63–2.65
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure, causing the original quartz grains to recrystallize and fuse together. This specimen appears water-worn from a river or beach environment.
Uses & applications
Used as a decorative aggregate in landscaping, as a building material in road construction, and occasionally for lapidary work or as polishing stones.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks in a landscape, forming resistant ridges. It is often confused with marble but can be distinguished because quartzite will not react with acid and can scratch glass.
Field identification & locations
Identify in the field by its extreme hardness (scratching glass or steel) and sugary texture. Commonly found in riverbeds, glacial deposits, and mountain ranges globally.
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