Chert (Jasper variation)

Physical Properties

Hardness: 6.5-7 on Mohs scale; Color: Brownish-tan; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Formation & Geological History

Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine environments; age can range from Precambrian to Holocene.

Uses & Applications

Historically used for making stone tools (arrowheads); currently used as abrasive media, road surfacing, or decorative landscape stone.

Geological Facts

Chert is so hard it can strike sparks against steel, which made it vital for flintlock firearms; it is essentially a non-banded form of chalcedony.

Field Identification & Locations

Identify by its extreme hardness (scratches glass) and smooth, shell-like (conchoidal) fracture surfaces; found globally in limestone and chalk beds.

Identified on: 5/2/2026

Mode: Standard