sedimentary

Chert / Jasper

Silicon Dioxide (SiO2)

Hardness: 6.5-7 Mohs scale. Color: Reddish-brown, tan, and cream-colored banding or mottling. Luster: Waxy to dull. Fracture: Conchoidal to uneven. Microcrystalline quartz structure.

Hardness: 6
Color: Reddish-brown, tan, and cream-colored banding or mottling
Luster: Waxy to dull

Identified July 24, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs scale. Color: Reddish-brown, tan, and cream-colored banding or mottling. Luster: Waxy to dull. Fracture: Conchoidal to uneven. Microcrystalline quartz structure.

Formation & geological history

Formed by precipitation of silica-rich fluids within sedimentary rock formations (such as limestone or shale) or through diagenetic replacement of organic material.

Uses & applications

Historically used for knapping arrowheads and stone tools due to conchoidal fracture. Modern uses include lapidary arts, landscaping, and aggregate.

Geological facts

Reddish coloration in chert or jasper is typically caused by inclusions of iron oxides (hematite or goethite). It is exceptionally durable and weather-resistant.

Field identification & locations

Identify by its hardness (scratches glass readily), smooth conchoidal fracture edges, waxy feel, and dense microcrystalline texture. Commonly found in sedimentary outcrops, river beds, and gravel deposits worldwide.