metamorphic
Quartzite Pebble
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, beige, or off-white with iron staining; Luster: Vitreous to waxy; Crystal structure: Hexagonal (trigonal); Cleavage: Indistinct/Conchoidal fracture; Specific gravity: 2.6-2.65.
- Hardness
- 7 on Mohs scale
- Color
- Tan, beige, or off-white with iron staining
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, beige, or off-white with iron staining; Luster: Vitreous to waxy; Crystal structure: Hexagonal (trigonal); Cleavage: Indistinct/Conchoidal fracture; Specific gravity: 2.6-2.65.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause the quartz grains to recrystallize and fuse together. This pebble has been subsequently rounded by water erosion through river or glacial action.
Uses & applications
Used in construction as crushed stone, as a decorative garden stone, and occasionally in glassmaking if pure enough. These water-worn pebbles are popular for landscaping and home decor.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock layers during mountain-building events, often forming the caps of ridges. It is harder than steel and can easily scratch a glass plate.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by a steel knife) and its grainy but fused texture. Commonly found in riverbeds, glacial deposits, and mountain ranges around the world.
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