sedimentary

Chert (Yellow Jasper/Flint)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale); Color: Tan, yellow, reddish-brown; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.65.

Hardness: 6
Color: Tan, yellow, reddish-brown
Luster: Waxy to dull

Identified July 1, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by the accumulation of siliceous remains of organisms or through the chemical precipitation of silica in groundwater. This specimen appears to be an iron-stained chert, often found in sedimentary deposits like limestone or as nodules in riverbeds.

Uses & applications

Historically used for making stone tools (arrowheads/scrapers) due to its sharp edges; used in jewelry as Jasper, and as industrial aggregate.

Geological facts

Chert has a conchoidal fracture, meaning it breaks like glass. It has been used by humans for millions of years to create fires and sharp-edged tools.

Field identification & locations

Identify in the field by its hardness (scratches glass), waxy luster, and its smooth, curved fracture surfaces. Commonly found in river gravels and ancient limestone beds.