sedimentary

Chert (Yellow Jasper variant)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale); Color: Yellowish-brown with white inclusions; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (has conchoidal fracture); Specific gravity: 2.6-2.7

Hardness: 6
Color: Yellowish-brown with white inclusions
Luster: Waxy to dull

Identified March 17, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the precipitation of silica from groundwater or the accumulation of siliceous organisms in marine environments. This specimen appears to be a water-worn river pebble, likely dating from various sedimentary epochs depending on local geology.

Uses & applications

Historically used for stone tools due to its sharp edges when fractured. Modern uses include decorative gravel, lapidary work (if polished), and as a minor gemstone (jasper).

Geological facts

Yellow chert/jasper is often colored by the presence of goethite or limonite (iron oxides). Because it is harder than glass and steel, it was a primary material for prehistoric 'flintknapping' to create scrapers and arrowheads.

Field identification & locations

Identify in the field by its hardness (it will scratch glass), waxy feel, and smooth, curved (conchoidal) breakage patterns. Typically found in riverbeds, glacial till, or as nodules within limestone/chalk formations.