metamorphic
Quartzite Pebble
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Off-white, beige, or grey; Luster: Vitreous to dull when weathered; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Off-white, beige, or grey
- Luster
- Vitreous to dull when weathered
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Physical properties
Hardness: 7 on Mohs scale; Color: Off-white, beige, or grey; Luster: Vitreous to dull when weathered; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
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 by fluvial or glacial erosion.
Uses & applications
Commonly used in construction aggregate, road ballast, and landscaping. High-purity quartzite is used to produce glass and metallurgical silicon.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, forming resistant ridges. It is often confused with marble, but quartzite will not fizz in contact with acid.
Field identification & locations
Identify by its ability to scratch glass and its grainy, sugary texture under a lens. It is found globally in areas with ancient mountain belts like the Appalachians or the Alps.
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