Chert (Jasper variety)

Physical Properties

Hardness: 6.5-7 (Mohs); Color: Brown, red, or tan; Luster: Dull to waxy; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & Geological History

Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine or groundwater environments. This specimen shows signs of river or water tumbling, resulting in its smooth, rounded shape.

Uses & Applications

Historically used for stone tools and arrowheads due to its sharp conchoidal fracture. Today used in jewelry (as jasper), landscaping, and as a collector's item.

Geological Facts

Chert is so hard it can scratch steel and produce sparks when struck against iron. Red and brown varieties are often specifically referred to as Jasper due to iron oxide inclusions.

Field Identification & Locations

Identify by its extreme hardness and smooth, waxy surface when broken. It cannot be scratched by a knife. Commonly found in riverbeds, glacial till, and sedimentary rock outcrops.

Identified on: 4/17/2026

Mode: Standard