sedimentary

Chert (Jasper variety)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Dark brown, reddish-brown, and black mottled; Luster: Dull to waxy; Structure: Cryptocrystalline; Fracture: Conchoidal.

Hardness: 6
Color: Dark brown, reddish-brown, and black mottled
Luster: Dull to waxy

Identified June 19, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Dark brown, reddish-brown, and black mottled; Luster: Dull to waxy; Structure: Cryptocrystalline; Fracture: Conchoidal.

Formation & geological history

Formed through the accumulation of silica-rich microfossils or chemical precipitation in sedimentary basins. This specimen shows a smooth, water-worn texture suggesting it was transported in a river or stream environment.

Uses & applications

Used primarily in lapidary work, jewelry making, and as a decorative stone. Historically used for making sharp-edged tools and weapons.

Geological facts

Jasper is an opaque variety of chert. The specific reddish and brown hues are usually caused by the presence of iron oxide (hematite or goethite) inclusions.

Field identification & locations

Identify in the field by its hardness (it will scratch glass), its waxy feel when smooth, and its characteristic curved (conchoidal) fracture pattern. Commonly found in riverbeds or as nodules in limestone.