metamorphic
Quartzite pebble
Quartzite (composed primarily of Quartz, SiO2)
Hardness: 7 on Mohs scale; Color: Reddish-brown due to iron oxide staining; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Color
- Reddish-brown due to iron oxide staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Reddish-brown due to iron oxide staining; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture).
Formation & geological history
Formed from the metamorphism of quartz sandstone under intense heat and pressure, typically during mountain-building events. These pebbles are often rounded by water erosion in riverbeds or coastal environments.
Uses & applications
Used as an abrasive, in construction as crushed stone, and sometimes as landscaping rock or for amateur stone tumbling.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the caps of ridges and mountains. A quick way to test it is that it will easily scratch glass but cannot be scratched by a steel knife.
Field identification & locations
Identified by its sugary texture and extreme hardness. Commonly found in river gravels and glacial deposits worldwide. Collectors look for unique colors caused by mineral impurities.
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