sedimentary

Chert (Yellow Jasper)

Cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

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

Identified July 1, 2026More sedimentary →

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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.