Chert (Yellow Jasper/River Pebble)

Physical Properties

Hardness: 6.5-7 (Mohs), Color: Yellowish-tan to grey, Luster: Waxy to vitreous when wet, Structure: Cryptocrystalline, Fracture: Conchoidal

Formation & Geological History

Formed by the precipitation of silica from groundwater or the accumulation of siliceous organisms in marine environments. This specimen shows significant rounding from fluvial (river) erosion.

Uses & Applications

Commonly used in landscaping, as a gemstone for tumbling, and historically used for stone tools due to its conchoidal fracture.

Geological Facts

Chert and jasper have been used by humans for hundreds of thousands of years to create arrowheads and scrapers because they break with extremely sharp edges.

Field Identification & Locations

Identify by its hardness (it will scratch glass), its smooth waxy feel, and the way it rounds into smooth 'potatoes' in riverbeds. Found globally in alluvial deposits.

Identified on: 4/29/2026

Mode: Standard