sedimentary

Chert (Jasper variety)

Silicon dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Tan, brown, and pink; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

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

Identified June 19, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Tan, brown, and pink; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

Formation & geological history

Formed through the accumulation of silica-rich microfossils or chemical precipitation in sedimentary environments. Can be found in various geological ages from Precambrian to Cenozoic.

Uses & applications

Used historically for stone tools and arrowheads; currently used for lapidary work, decorative landscaping, and as a polishing media.

Geological facts

This specimen features a distinct 'eye' or 'orb' pattern, likely caused by mineral replacement or a concretion during the formation phase. Chert is essentially a non-banded form of chalcedony.

Field identification & locations

Identify in the field by its smooth, waxy feel and characteristic curved (conchoidal) fractures. It will easily scratch glass. Found globally in limestone and dolomite beds.