Red Chert (Jasper)

Physical Properties

Hardness: 6.5-7 (Mohs scale); Color: Red/rust due to iron oxide; Luster: Waxy to dull; Crystal structure: Hexagonal (cryptocrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

Formation & Geological History

Formed through the accumulation of silica-rich organic remains (like radiolaria) or chemical precipitation in marine environments. The reddish tint specifically comes from the inclusion of hematite or other iron oxides during formation.

Uses & Applications

Historically used for making stone tools (flintknapping); currently used in jewelry (cabochons), as decorative landscaping stones, and popular for rock tumbling.

Geological Facts

Jasper has been used by humans for thousands of years; it was a favorite gem in the ancient world, mentioned in biblical texts and used in Babylonian seals.

Field Identification & Locations

Identify in the field by its smooth, waxy texture, inability to be scratched by a steel knife, and characteristic 'clinking' sound when struck against other hard rocks. Commonly found in riverbeds and glacial deposits.

Identified on: 4/15/2026

Mode: Standard