sedimentary

Chert (Jasper variety)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale); Color: reddish-brown to tan; Luster: dull to waxy; Structure: cryptocrystalline; Cleavage: none (conchoidal fracture); Specific gravity: 2.65.

Hardness: 6
Color: reddish-brown to tan
Luster: dull to waxy

Identified July 4, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: reddish-brown to tan; Luster: dull to waxy; Structure: cryptocrystalline; Cleavage: none (conchoidal fracture); Specific gravity: 2.65.

Formation & geological history

Formed through the accumulation of silica-rich microfossils or chemical precipitation from silica-rich fluids within sedimentary rock layers. Most common in ancient marine environments.

Uses & applications

Historically used for stone tools (knapping); today used in landscaping, decorative stone, and lapidary arts for jewelry and tumbling.

Geological facts

Chert is so hard it can strike sparks from steel. Specimens with vibrant red coloring due to iron inclusions are specifically referred to as Jasper.

Field identification & locations

Identify in the field by its smooth, waxy feel and shell-like (conchoidal) fracture patterns. Frequently found in stream beds or within limestone and dolomite formations.