sedimentary

Chert (Yellow or Ochre Jasper variant)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale; Color: Opaque yellowish-brown to tan; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 6
Color: Opaque yellowish-brown to tan
Luster: Waxy to dull

Identified March 15, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Opaque yellowish-brown to tan; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Formation & geological history

Formed through the accumulation of silica-rich fluids in sedimentary basins or the replacement of limestone. This specimen appears water-worn or tumbled, likely from a fluvial (river) environment, dating from various eras depending on the local bedrock.

Uses & applications

Historically used for stone tools (knapping) due to its sharp edges; modernly used in landscaping, as a minor gemstone (jasper), or as an abrasive.

Geological facts

Chert is so durable that it often survives long after the surrounding rock has weathered away. Early humans prioritized this material over almost any other for crafting arrowheads and scrapers.

Field identification & locations

Identify in the field by its smooth, waxy texture and inability to be scratched by a steel knife. It will also spark when struck against steel. Commonly found in gravel pits, riverbeds, and as nodules within limestone outcrops.