Chert (Jasper/Flint variety)

Physical Properties

Hardness: 7 on Mohs scale; Color: Gray with yellow-orange limonitic staining; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Formation & Geological History

Formed through the accumulation of silica-rich microfossils or chemical precipitation in marine or groundwater environments. This pebble shows significant river or beach abrasion, rounding its edges over thousands of years.

Uses & Applications

Historically used for making stone tools (arrowheads). Modern uses include landscaping, as decorative river stones, and occasionally as lapidary material for jewelry if the patterns are unique.

Geological Facts

Chert is so durable that it often survives long after the surrounding rock has weathered away. The orange-yellow bands in this specimen are caused by iron oxide impurities that seeped into the micro-fissures of the stone.

Field Identification & Locations

Identify by its extreme hardness (cannot be scratched by a steel knife) and its smooth, rounded 'river stone' texture. Commonly found in riverbeds, glacial tills, and along coastlines.

Identified on: 4/25/2026

Mode: Standard