sedimentary

Chert (Jasper variety)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Brown, reddish-brown, tan; Luster: Dull to waxy (looks vitreous when wet); Crystal Structure: Microcrystalline/Cryptocrystalline quartz; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 6
Color: Brown, reddish-brown, tan
Luster: Dull to waxy (looks vitreous when wet)

Identified April 28, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like radiolaria or diatoms) or chemical precipitation from silica-rich fluids in sedimentary basins. This specimen shows significant rounding, suggesting it was transport by water (alluvial) in a riverbed.

Uses & applications

Historically used for stone tools due to sharp edges; currently used for lapidary work (cabochons), landscaping, and as a collector's item.

Geological facts

Jasper is an opaque variety of chert. Because of its extreme hardness and durability, it often survives long-distance transport in rivers and remains largely intact while softer rocks erode away.

Field identification & locations

Identify in the field by its hardness (it will scratch glass), its smooth 'waxy' texture, and its characteristic conchoidal (shell-like) fracture patterns. Frequently found in gravel bars of rivers and along coastlines.