sedimentary

Chert (Jasper)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs); Color: Brownish-tan to reddish-brown; Luster: Waxy to dull; Break: Conchoidal (shell-like) fracture; Structure: Microcrystalline quartz.

Hardness: 6
Color: Brownish-tan to reddish-brown
Luster: Waxy to dull

Identified July 2, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs); Color: Brownish-tan to reddish-brown; Luster: Waxy to dull; Break: Conchoidal (shell-like) fracture; Structure: Microcrystalline quartz.

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine or groundwater environments. This specimen shows iron oxide staining giving it its earthy brown color.

Uses & applications

Historically used for stone tools and weapons due to its sharp edges; modern uses include landscaping, jewelry (as Jasper), and as a raw material for decorative items.

Geological facts

This material is often called 'Jasper' when it is opaque and colored by mineral impurities like iron. It is one of the most durable sedimentary rocks and survives long after surrounding limestone has weathered away.

Field identification & locations

Identify in the field by its hardness (it will scratch glass), its smooth waxy feel on fresh surfaces, and its signature curved fracture patterns. Commonly found in riverbeds or as nodules within limestone.