Chert (Yellow Jasper variant)

Physical Properties

Hardness: 6.5-7 on Mohs scale; Color: Ocher, tan, brown; Luster: Dull to waxy; Structure: Cryptocrystalline/Amorphous appearance; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Formation & Geological History

Formed via the accumulation of silica-rich microfossils or chemical precipitation from hydrothermal fluids in sedimentary basins. The yellow-brown hue comes from goethite or iron oxide inclusions.

Uses & Applications

Historically used for stone tools (knapping); currently used for decorative pebbles, jewelry cabochons, and as a durable material in landscaping.

Geological Facts

Commonly known as 'Jasper' when opaque and colored. It has been used by humans for hundreds of thousands of years to create sharp-edged tools due to its glass-like fracturing pattern.

Field Identification & Locations

Identify by its smooth, waxy texture and inability to be scratched by a steel knife. It often occurs as nodules in limestone or as smooth, water-worn river cobbles.

Identified on: 5/13/2026

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