sedimentary

Chert (Yellow Jasper)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs; Color: Pale yellow to mustard yellow with cream patches; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7.

Hardness: 6
Color: Pale yellow to mustard yellow with cream patches
Luster: Waxy to dull

Identified July 14, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Pale yellow to mustard yellow with cream patches; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7.

Formation & geological history

Formed via the precipitation of silica from groundwater or the accumulation of silica-rich organic remains in sedimentary basins. The yellow hue is typically caused by goethite or iron oxide inclusions.

Uses & applications

Commonly used for lapidary work, jewelry (beads/cabochons), and historically for stone tools due to its sharp fracture. It is also used in decorative landscaping.

Geological facts

Chert has been used by humans for millions of years to make arrowheads and scrapers. Yellow varieties are often categorized as 'Jasper' when they are opaque and colorful.

Field identification & locations

Identified by its extreme hardness (cannot be scratched by a steel knife) and waxy, smooth texture compared to the surrounding rock. Often found in riverbeds or limestone deposits throughout the Midwestern USA and coastal regions.