metamorphic
Quartzite Pebble
Quartzite (SiO2)
Hardness: 7 (Mohs scale); Color: White to off-white with gray streaks; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None; Specific gravity: 2.6-2.7.
- Hardness
- 7 (Mohs scale)
- Color
- White to off-white with gray streaks
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: White to off-white with gray streaks; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None; Specific gravity: 2.6-2.7.
Formation & geological history
Formed from the metamorphism of quartz sandstone under intense heat and pressure, typically in orogenic belts. This specific specimen has been further shaped and smoothed by fluvial or coastal erosion.
Uses & applications
Commonly used in construction as railway ballast, as an abrasive, and in road surfacing. Polished pebbles are used for landscaping and decorative housewares.
Geological facts
Quartzite is so hard that it will scratch glass and even steel. It is one of the most durable rocks on the Earth's surface and often remains as mountain peaks after softer rocks erode away.
Field identification & locations
Identify in the field by its hardness and granular, sugary appearance on a fresh break. It will not fizz with acid (unlike marble). Commonly found in riverbeds and on beaches worldwide.
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