sedimentary

Chert (Yellow Jasper variant)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale. Color: Opaque yellow, tan, and brown. Luster: Waxy to dull. Crystal Structure: Trigonal (microcrystalline/cryptocrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6-2.7.

Hardness: 6
Color: Opaque yellow, tan, and brown
Luster: Waxy to dull

Identified June 14, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed primarily through the chemical precipitation of silica-rich fluids in sedimentary environments or through the replacement of limestone. This specimen likely originated from hydrothermal activity or secondary silica deposition in cracks.

Uses & applications

Historically used for stone tools (knapping) due to its sharp edges. Modern uses include jewelry (cabochons), landscaping decorative stone, and as a collector's specimen.

Geological facts

Chert is so durable that it often survives as stream gravel long after the surrounding rock has weathered away. Early humans transitioned from using basic stones to chert and flint because of their predictable fracture patterns.

Field identification & locations

Identify in the field by its waxy luster, extreme hardness (it will scratch glass), and shell-like (conchoidal) fractures. Often found in riverbeds or within limestone outcrops.