sedimentary
Chert (specifically Red Chert/Jasper)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown with translucent areas; Luster: Waxy to vitreous; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Color
- Reddish-brown with translucent areas
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown with translucent areas; Luster: Waxy to vitreous; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed primarily from the accumulation of silica-rich microfossils like radiolaria or diatoms on the seafloor, later undergoing lithification. Red hues indicate iron oxide inclusions.
Uses & applications
Historically used for stone tools and arrowheads due to its sharp edges; modernly used as a decorative stone, in jewelry (when polished), and as road ballast.
Geological facts
Chert is one of the most durable sedimentary rocks and was among the first materials used by prehistoric humans to create fire and weaponry.
Field identification & locations
Identify by its conchoidal (shell-like) fracture, waxy surface, and extreme hardness (it will scratch glass). Commonly found in sedimentary basins or as nodules in limestone.
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