sedimentary
Chert (Yellow Jasper)
Cryptocrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: Yellowish-brown to tan; Luster: Dull to waxy; Structure: Microcrystalline; Fracture: Conchoidal; Cleavage: None
- Hardness
- 6
- Color
- Yellowish-brown to tan
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Yellowish-brown to tan; Luster: Dull to waxy; Structure: Microcrystalline; Fracture: Conchoidal; Cleavage: None
Formation & geological history
Formed through the accumulation of silica-rich microfossils like diatoms or radiolarians, or via chemical precipitation from silica-saturated fluids in limestone or ocean floor environments.
Uses & applications
Historically used for stone tools and arrowheads; currently used for lapidary work, jewelry (as 'Jasper'), and as a high-durability landscaping or road material.
Geological facts
Chert is so hard it can scratch steel and was used by ancient humans to create sparks for fire and sharp edges for hunting.
Field identification & locations
Identify by its 'flint-like' waxy texture, curved (conchoidal) breaks, and hardness. Often found in riverbeds or as nodules within limestone outcrops.
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