sedimentary
Chert / Pink Flint
Cryptocrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Pink, tan, and creamy white; Luster: Waxy to vitreous; Crystal Structure: Hexagonal (microscopic); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Pink, tan, and creamy white
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: Pink, tan, and creamy white; Luster: Waxy to vitreous; Crystal Structure: Hexagonal (microscopic); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like diatoms) or chemical precipitation in sedimentary basins. The pink hue often comes from trace iron oxide inclusions. Found in rock layers ranging from Precambrian to recent.
Uses & applications
Historically used for stone tools and weapons due to sharp edges; currently used for lapidary work, jewelry (cabochons), road surfacing, and as a component in ceramics and glass.
Geological facts
Chert was one of the first materials traded globally by early humans. This specific specimen shows conchoidal (shell-like) fracturing, a key trait that allows it to be knapped into arrowheads.
Field identification & locations
Identify in the field by its hardness (scratches glass), waxy feel, and sharp, curved fracture patterns. Commonly found in limestone beds or as nodules in riverbeds across the United States, especially in the Midwest and South.
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