metamorphic
Quartzite (River Pebble)
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 (Mohs scale); Color: Grayish-translucent with white internal fractures; Luster: Vitreous to waxy; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.63 - 2.65
- Hardness
- 7 (Mohs scale)
- Color
- Grayish-translucent with white internal fractures
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 (Mohs scale); Color: Grayish-translucent with white internal fractures; Luster: Vitreous to waxy; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.63 - 2.65
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. Under intense heat and pressure, original sand grains recrystallize and fuse together. The rounded shape indicates significant water erosion, likely from a river or glacial deposit, spanning millions of years.
Uses & applications
Common industrial uses include construction aggregate, road ballast, and glass manufacturing. This specific specimen has value for mineral collecting, lapidary tumbling, and educational purposes.
Geological facts
Quartzite is so durable that it often survives intense weathering that destroys other rocks. It is harder than a steel knife blade and can scratch glass easily. In ancient times, it was occasionally used to create stone tools when flint was unavailable.
Field identification & locations
Identify in the field by its sugary texture on broken surfaces and its ability to scratch glass. It is commonly found in riverbeds, glacial tills, and mountain ranges. This specimen is a typical 'river rock' found worldwide.
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