metamorphic
Quartzite Pebble
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: white, grey, beige with brownish iron staining; Luster: vitreous to dull; Crystal Structure: Trigonal (microcrystalline); Cleavage: none (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Color
- white, grey, beige with brownish iron staining
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: white, grey, beige with brownish iron staining; Luster: vitreous to dull; Crystal Structure: Trigonal (microcrystalline); Cleavage: none (conchoidal fracture).
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically in orogenic belts. This specific specimen has been rounded and smoothed by water transport in a river or coastal environment.
Uses & applications
Used as decorative gravel, in landscaping, and as a source of silica for glassmaking. Smooth pebbles are popular in aquarium decor and stone massage therapy.
Geological facts
Quartzite is so tough that it usually breaks through the quartz grains rather than around them, unlike its parent sandstone. It is one of the most durable rocks on the Earth's surface.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel knife) and lack of reaction to acid. Commonly found in riverbeds, glacial tills, and beaches.
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