sedimentary

Chert (Jasper)

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Tan, beige, and brown with orange-yellow oxidation; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.65

Hardness: 6
Color: Tan, beige, and brown with orange-yellow oxidation
Luster: Waxy to dull

Identified July 6, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine environments. Often found as nodules within limestone or chalk beds, or as bedded deposits.

Uses & applications

Historically used for stone tools (knapping). Currently used as decorative landscaping stones, aggregate in construction, and for lapidary work (polishing/tumbling).

Geological facts

Because of its high silica content and microcrystalline structure, chert breaks with a very sharp edge. It was one of the most important minerals for early humans to create arrowheads and scrapers.

Field identification & locations

Identify in the field by its hardness (will scratch glass), smooth waxy feel on breaks, and characteristic shell-like (conchoidal) fracture pattern. Commonly found in riverbeds and limestone outcrops.