metamorphic
Quartzite (Water-Worn)
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Off-white to beige with tan staining; Luster: Vitreous to dull; Crystal structure: Non-foliated granoblastic; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Off-white to beige with tan staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Off-white to beige with tan staining; Luster: Vitreous to dull; Crystal structure: Non-foliated granoblastic; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause quartz grains to recrystallize and fuse. This specific specimen has been smoothed by water transport (alluvial processes).
Uses & applications
Used primarily in construction as crushed stone or ballast. High-purity quartzite is used to produce glass and silicon metal. Rounded river stones like this are often used in decorative landscaping.
Geological facts
Quartzite is so tough that it often outlasts the mountains it forms, remaining as weather-resistant caprocks. It is harder than steel and will easily scratch glass.
Field identification & locations
Identify in the field by its extreme hardness and sugary, crystalline texture often visible on fresh breaks. Found globally in riverbeds or glacial tills. Collectors look for unique shapes or clarity.
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