sedimentary
Chert (often called Flint or Jasper)
Silicon Dioxide (SiO2)
Hardness: 7 on Mohs scale; Color: variegated gray, reddish-brown, and white; Luster: waxy to vitreous; Crystal structure: Cryptocrystalline; Cleavage: none (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- variegated gray, reddish-brown, and white
- Luster
- waxy to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: variegated gray, reddish-brown, and white; Luster: waxy to vitreous; Crystal structure: Cryptocrystalline; Cleavage: none (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed by the accumulation of siliceous remains of organisms or chemical precipitation of silica in sedimentary environments, often found as nodules in limestone or chalk beds.
Uses & applications
Historically used for stone tools (knapping); currently used in jewelry (as Jasper), lapidary art, building stone, and road surfacing materials.
Geological facts
Chert was one of the most important resources for prehistoric humans because it breaks with a conchoidal fracture, creating sharp edges for arrowheads and knives.
Field identification & locations
Look for a smooth, waxy surface and extremely sharp edges when broken. It is harder than steel and will scratch a glass plate. Commonly found in riverbeds and limestone outcrops.
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