sedimentary

Chert (Jasper)

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 (Mohs scale), Color: Red, brown, and yellowish-tan, Luster: Waxy to dull, Structure: Cryptocrystalline, Fracture: Conchoidal (shell-like curves), Specific Gravity: 2.6-2.7

Hardness: 6

Identified June 22, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale), Color: Red, brown, and yellowish-tan, Luster: Waxy to dull, Structure: Cryptocrystalline, Fracture: Conchoidal (shell-like curves), Specific Gravity: 2.6-2.7

Formation & geological history

Formed via the accumulation of silica-rich fluids in sedimentary environments or by the replacement of calcium carbonate. This specimen likely formed as a nodule in limestone or as a byproduct of volcanic secondary mineralization.

Uses & applications

Historically used for stone tools (knapping) due to its sharp edges; currently used for lapidary work, jewelry (especially when patterned as Jasper), and as a collector's specimen.

Geological facts

Chert is so hard it can create sparks when struck against steel. Prehistoric humans highly valued this material for making arrowheads and spear points because of its predictable fracture patterns.

Field identification & locations

Identify in the field by its waxy appearance and smooth, curved fracture surfaces. It cannot be scratched by a steel knife. Commonly found in riverbeds, glacial deposits, and embedded in limestone outcrops.