sedimentary
Chert (Weathered)
Chert (Microcrystalline Quartz, SiO2)
Hardness: 7 (Mohs scale); Color: White, cream, tan; Luster: Waxy to dull (weathered); Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 7 (Mohs scale)
- Color
- White, cream, tan
- Luster
- Waxy to dull (weathered)
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Physical properties
Hardness: 7 (Mohs scale); Color: White, cream, tan; Luster: Waxy to dull (weathered); Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine environments. This specimen was found near Louisville, Kentucky, a region rich in Mississippian and Devonian limestone layers where chert nodules are frequently weathered out of the parent rock.
Uses & applications
Historically used for stone tools and arrowheads due to conchoidal fracture; currently used in construction aggregate, road base, and as decorative gravel.
Geological facts
Chert is extremely durable and chemically stable, often remaining in the soil long after the limestone it formed in has eroded away. Historically, high-quality chert was a major trade commodity for indigenous populations.
Field identification & locations
Identify in the field by its hardness (it will scratch glass and steel), waxy feel, and smooth, curved fracture surfaces. Very common in the Ohio River Valley region (Kentucky/Indiana border).
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