sedimentary
Chert (Flint)
Microcrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Brown, tan, gray; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Brown, tan, gray
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Brown, tan, gray; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed from the accumulation of silica-rich organic remains or through the replacement of limestone. Found in beds or as nodules within sedimentary rock layers.
Uses & applications
Historically used for stone tools and starting fires. Today used in construction aggregates, decor, and occasionally as semi-precious gemstones.
Geological facts
Chert has been used by humans for over 2 million years to make arrowheads and scrapers due to its predictable conchoidal fracturing.
Field identification & locations
Identify by its smooth, waxy feel and sharp, glass-like edges when broken. It will scratch glass and won't react with acid.
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