metamorphic
Quartzite Cobble
Metamorphic Quartzite (SiO2)
Hardness: 7 (Mohs scale); Color: Tan, beige, off-white; Luster: Dull/Waxy (weathered); Crystal Structure: Granular/Crystalline; Cleavage: None (conchoidal fracture).
- Hardness
- 7 (Mohs scale)
- Color
- Tan, beige, off-white
- Luster
- Dull/Waxy (weathered)
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Physical properties
Hardness: 7 (Mohs scale); Color: Tan, beige, off-white; Luster: Dull/Waxy (weathered); Crystal Structure: Granular/Crystalline; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed when quartz-rich sandstone is subjected to intense heat and pressure (metamorphism). The specimen appears to be water-worn into a cobble shape, likely found in a riverbed or glacial deposit.
Uses & applications
Used in construction for road ballast, crushed stone, and landscaping. High-quality quartzite is used as a dimension stone or in glass making.
Geological facts
Quartzite is one of the most durable rocks on the Earth's surface. The wavy patterns seen on the surface are likely relict bedding planes from its original sedimentary state or mineral veins.
Field identification & locations
Identify by its hardness (it will scratch glass easily) and its sugary, granular appearance when broken. It is a common find in global regions with ancient metamorphic basements.
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