sedimentary

Chert / Jasper

Silicon Dioxide (SiO2)

Hardness: 6.5-7 Mohs; Color: reddish-brown with white/gray inclusions; Luster: waxy to vitreous; Crystal structure: cryptocrystalline (microscopic quartz); Cleavage: none, conchoidal fracture.

Hardness: 6
Color: reddish-brown with white/gray inclusions
Luster: waxy to vitreous

Identified June 19, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: reddish-brown with white/gray inclusions; Luster: waxy to vitreous; Crystal structure: cryptocrystalline (microscopic quartz); Cleavage: none, conchoidal fracture.

Formation & geological history

Formed through the accumulation of silica-rich microfossils or chemical precipitation in marine or volcanic environments; often found in sedimentary beds or as nodules in limestone.

Uses & applications

Historically used for stone tools and arrowheads; modernly used as decorative landscape stone and occasionally for lapidary work/jewelry.

Geological facts

This specimen shows the characteristic waxy luster and jagged fracture lines of microcrystalline quartz. It belongs to the chalcedony family.

Field identification & locations

Identify by its ability to scratch glass and its smooth, shell-like (conchoidal) fracture surfaces that are sharp to the touch. Common worldwide in sedimentary basins.