sedimentary

Chert (Yellow Jasper variant)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Yellowish-brown to tan (stained by iron oxides); Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture)

Hardness: 7 on Mohs scale
Color: Yellowish-brown to tan (stained by iron oxides)
Luster: Waxy to dull

Identified July 10, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Yellowish-brown to tan (stained by iron oxides); Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture)

Formation & geological history

Formed via the accumulation of silica-rich microfossils or chemical precipitation in sedimentary basins. Diagenetic processes replace original limestone or chalk with silica over millions of years.

Uses & applications

Historically used for stone tools (knapping) due to sharp edges; currently used for decorative gravel, landscaping, and lapidary tumbling.

Geological facts

Chert is so hard it can scratch glass and steel. It was one of the most important minerals for early humans to create arrowheads and scrapers.

Field identification & locations

Identify by its characteristic conchoidal (shell-like) fracture patterns and ability to scratch glass. Found globally in limestone layers or as weathered nodules in stream beds.