sedimentary
Chert (Pink variety/Jasper)
Silicon Dioxide (SiO2)
Hardness: 6.5-7 (Mohs scale); Color: Pink to reddish-brown; Luster: Waxy to dull; Crystal structure: Microcrystalline/cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 6
- Color
- Pink to reddish-brown
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Pink to reddish-brown; Luster: Waxy to dull; Crystal structure: Microcrystalline/cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like radiolarians or diatoms) or by chemical precipitation from groundwater within limestone or chalk beds. Often dated from the Paleozoic to Mesozoic eras.
Uses & applications
Used historically for stone tools and weapons due to its sharp edges; modern uses include decorative lapidary work, jewelry (cabochons), and landscaping stone.
Geological facts
Chert is so hard it can strike sparks against steel, making it a primary component for 'flintlock' mechanisms. Pink varieties often get their color from trace amounts of iron oxide impurities.
Field identification & locations
Identify in the field by its smooth, shell-like (conchoidal) fracture and its ability to scratch glass. It is commonly found as nodules within limestone or as bedded layers in marine sedimentary rocks.
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