sedimentary
Chert (Quartzite Pebble)
Microcrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, cream, white with iron staining; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Tan, cream, white with iron staining
- Luster
- Dull to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, cream, white with iron staining; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed primarily as a sedimentary rock composed of microscopic quartz crystals. This specific specimen is a water-worn river or beach pebble, smoothed by mechanical erosion over thousands of years within high-energy water environments.
Uses & applications
Historically used for stone tools (arrowheads). Modern uses include construction aggregate, landscaping, and lapidary tumbling for hobbyists.
Geological facts
Chert is extremely durable and chemically stable, allowing it to survive long-distance transport in rivers. It often contains microfossils of radiolaria or diatoms.
Field identification & locations
Identify in the field by its hardness (it will scratch glass) and its smooth, rounded 'potato-like' appearance when found as a pebble. Commonly found in riverbeds and on beaches worldwide.
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