metamorphic
Quartzite Cobble
Quartzite (primarily SiO2)
AI-generated identification · may be incorrectHardness: 7 on Mohs scale; Color: Reddish-brown/Tan; Luster: Dull to vitreous; Crystal structure: Granular/Microcrystalline; High specific gravity (2.6-2.7).
- Hardness
- 7 on Mohs scale
- Color
- Reddish-brown/Tan
- Luster
- Dull to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: Reddish-brown/Tan; Luster: Dull to vitreous; Crystal structure: Granular/Microcrystalline; High specific gravity (2.6-2.7).
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure, where individual grains recrystallize into a dense interlaced structure. This specimen shows significant rounding from river or coastal erosion.
Uses & applications
Used as a decorative landscape stone, in construction as crushed stone or ballast, and as a durable material for historical toolmaking.
Geological facts
Quartzite is so strong that when it breaks, the fracture goes through the quartz grains rather than around them, unlike its parent stone sandstone.
Field identification & locations
Identify by its hardness (will scratch glass) and lack of visible grains typical of sandstone. Commonly found in riverbeds, glacial tills, and coastal beaches.
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