sedimentary

Chert (Yellow Jasper)

Silicon Dioxide (SiO2) - Microcrystalline Quartz

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale); Color: Ocher yellow to brownish; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 6
Color: Ocher yellow to brownish
Luster: Waxy to dull

Identified May 7, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: Ocher yellow to brownish; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed through the accumulation of silica-rich fluids or biological remains (like radiolarians) in sedimentary basins, often replacing limestone or forming as nodules. Can be hundreds of millions of years old.

Uses & applications

Historically used for stone tools and arrowheads due to sharp fracturing; currently used in lapidary work, jewelry, and as decorative river stone.

Geological facts

This specimen is often called 'Yellow Jasper' when it is opaque and colored by iron oxides (limonite/goethite). It is one of the most durable rocks found in river beds.

Field identification & locations

Identify by its 'waxy' texture and conchoidal (shell-like) fracture pattern. It will easily scratch glass. Commonly found in river gravels, desert pavements, and limestone outcrops.