Chert (Jasper variety)

Physical Properties

Hardness: 6.5-7 on Mohs scale; Color: Yellowish-brown, tan, with darker stripes; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline quartz; Cleavage: None (conchoidal fracture).

Formation & Geological History

Formed through the accumulation of silica-rich microfossils or chemical precipitation of silica in marine or groundwater environments. This specimen appears as a water-worn pebble, likely from a river or glacial deposit.

Uses & Applications

Used historically for stone tools due to sharp edges; currently used for lapidary work, jewelry (beads/cabochons), and as aquarium or decorative stone.

Geological Facts

Chert is so durable that it can survive long-distance transport in rivers and glacial till. High-quality colored chert is often referred to as Jasper.

Field Identification & Locations

Identify by its hardness (cannot be scratched by a steel knife) and its smooth, waxy texture. Commonly found in gravel pits, river beds, and coastal erosion zones.

Identified on: 4/25/2026

Mode: Standard