metamorphic
Quartzite Pebble
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: white to off-white; Luster: vitreous or dull (water-worn); Crystal structure: Trigonal (microcrystalline); Cleavage: None/Conchoidal fracture.
- Hardness
- 7 on Mohs scale
- Color
- white to off-white
- Luster
- vitreous or dull (water-worn)
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Physical properties
Hardness: 7 on Mohs scale; Color: white to off-white; Luster: vitreous or dull (water-worn); Crystal structure: Trigonal (microcrystalline); Cleavage: None/Conchoidal fracture.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, usually during mountain-building events. This specimen has been smoothed by river or beach water erosion.
Uses & applications
Commonly used in construction as railway ballast, crushed stone for road aggregate, and as decorative landscaping stones. Higher purity varieties are used to produce silica sand.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock in weathering processes, resulting in the rounded pebbles frequently found in riverbeds. It is often harder than the steel of a knife blade.
Field identification & locations
Identify by its ability to scratch glass and lack of reaction to acid (unlike limestone). Commonly found in glaciated areas, riverbeds, and mountainous regions like the Appalachians or Alps.
