metamorphic
Quartzite Pebble
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 on Mohs scale; Color: Off-white to light tan; Luster: Vitreous to dull/waxy; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Off-white to light tan
- Luster
- Vitreous to dull/waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Off-white to light tan; Luster: Vitreous to dull/waxy; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events. This specific specimen has been further shaped and smoothed by water erosion in a river or coastal environment.
Uses & applications
Commonly used in construction as aggregate, in landscaping, and sometimes as a source of silica for glass manufacturing. Smooth river pebbles are highly popular for decorative landscaping.
Geological facts
Quartzite is so durable that it often survives millions of years of erosion that wears away surrounding softer rocks. It is harder than steel and will scratch a glass plate easily.
Field identification & locations
Identify in the field by its superior hardness (cannot be scratched by a steel knife) and its grainy, sandpaper-like texture that has been fused into a crystalline mass. Commonly found in riverbeds and glacial deposits.
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