sedimentary

Chert (Jasper/Chalcedony)

Silicon dioxide (SiO2) - Microcrystalline quartz

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs scale; Color: Tan, brown, and cream; Luster: Waxy to dull; Breakdown: Conchoidal fracture; Transparency: Opaque to translucent

Hardness: 6
Color: Tan, brown, and cream
Luster: Waxy to dull

Identified July 2, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs scale; Color: Tan, brown, and cream; Luster: Waxy to dull; Breakdown: Conchoidal fracture; Transparency: Opaque to translucent

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in sedimentary environments. Can be found in nodules within limestone or as bedded deposits.

Uses & applications

Historically used for stone tools (knapping) due to its sharp edges; currently used for lapidary work, jewelry, and as a collector's specimen.

Geological facts

Chert is one of the most common materials used by prehistoric humans for arrowheads and spear tips because it fractures like glass to create razor-sharp edges.

Field identification & locations

Identify by its waxy appearance, extreme hardness (it will scratch glass), and its smooth, curved conchoidal fractures. Commonly found in riverbeds or limestone outcrops.