sedimentary

Chert (Yellow Jasper)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale); Color: Yellow (due to iron oxide inclusions), tan, or mustard; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.65.

Hardness: 6
Color: Yellow (due to iron oxide inclusions), tan, or mustard
Luster: Dull to waxy

Identified February 11, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich fluids or the replacement of limestone. It typically forms in marine environments where silica-rich organic remains (like radiolaria or diatoms) recrystallize over millions of years.

Uses & applications

Historical use in stone tools (arrowheads, scrapers) due to its sharp edges; modern uses include lapidary work, jewelry (cabs), and as a decorative landscaping stone.

Geological facts

Yellow chert or jasper has been used by humans for over 100,000 years. Because of its extreme hardness and ability to hold a sharp edge, it was a primary material for prehistoric survival tools.

Field identification & locations

Identify in the field by its smooth, shell-like (conchoidal) fracture and its ability to scratch glass. Widely found in riverbeds, glacial tills, and within limestone outcrops. Collectors look for pieces with unique patterns or deep coloration.