metamorphic
Quartzite Pebble
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale (scratches glass); Color: milky white to light grey with a tan vein; Luster: vitreous to waxy when polished; Crystal structure: Trigonal/Hexagonal (microcrystalline/granular); Cleavage: none (conchoidal fracture).
- Hardness
- 7 on Mohs scale (scratches glass)
- Color
- milky white to light grey with a tan vein
- Luster
- vitreous to waxy when polished
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Physical properties
Hardness: 7 on Mohs scale (scratches glass); Color: milky white to light grey with a tan vein; Luster: vitreous to waxy when polished; Crystal structure: Trigonal/Hexagonal (microcrystalline/granular); Cleavage: none (conchoidal fracture).
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure reciprocal to tectonic activity cause individual quartz grains to recrystallize and fuse together. This specific specimen has been smoothed and rounded by river or beach erosion.
Uses & applications
Used industrially as a source of silica, in construction as crushed stone or decorative landscaping gravel, and occasionally for lapidary work or 'worry stones'.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock in high-energy environments like riverbeds. It is often confused with marble, but unlike marble, it will not fizz when exposed to acid and is much harder.
Field identification & locations
Identify in the field by its inability to be scratched by a steel knife and its granular, sugary appearance on a fresh break. Commonly found in mountainous regions or as water-worn cobbles in river basins drainage areas.
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