metamorphic
Quartzite river pebble
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Tan to milky white with grey-brown staining; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None/Conchoidal fracture.
- Hardness
- 7 on Mohs scale
- Color
- Tan to milky white with grey-brown staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan to milky white with grey-brown staining; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None/Conchoidal fracture.
Formation & geological history
Formed when quartz-rich sandstone is subjected to intense heat and pressure during regional metamorphism. This specific piece has been smoothed and rounded by fluvial processes (river action) over thousands of years.
Uses & applications
Quartzite is used in construction as stabilizer for road beds, in glass making (if pure), and as decorative landscaping stone. Polished pebbles are often used in rock tumblers or as 'worry stones'.
Geological facts
Quartzite is so tough it often survives long after the surrounding rocks have eroded away. It is usually harder than the steel blade of a knife and will easily scratch glass.
Field identification & locations
Identified by its extreme hardness, granular texture, and lack of reaction to acid. Often found in riverbeds, glacial deposits, and mountain ranges. This specimen shows typical 'desert varnish' or mineral staining on one side.
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