sedimentary

Chert (Jasper)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale); Color: Brownish-red to mustard yellow (hematite/goethite inclusions); Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Hardness: 6
Luster: Waxy to dull

Identified April 12, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like diatoms) or chemical precipitation from groundwater within sedimentary layers. These specimens appear to be stream-rounded pebbles.

Uses & applications

Historically used for stone tools due to sharp fracture edges; currently used for decorative stone, lapidary tumbling, and architectural gravel.

Geological facts

Chert has been used by humans for over 2 million years to create spear points and arrows. These specific specimens are commonly referred to as 'yellow jasper' or 'river jasper' when found in alluvial deposits.

Field identification & locations

Identify in the field by its hardness (it will scratch glass), waxy feel, and smooth, curved (conchoidal) breaks. Found in riverbeds, gravel pits, and ancient sea beds globally.