sedimentary

Chert / Jasper

Cryptocrystalline Quartz (SiO2)

Hardness: 6.5-7 (Mohs scale), Color: Rusty brown to orange-red due to iron inclusions, Luster: Waxy to dull, Crystal Structure: Microcrystalline, Cleavage: None (conchoidal fracture), SG: 2.6

Hardness: 6

Identified June 6, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale), Color: Rusty brown to orange-red due to iron inclusions, Luster: Waxy to dull, Crystal Structure: Microcrystalline, Cleavage: None (conchoidal fracture), SG: 2.6

Formation & geological history

Formed from the precipitation of silica in sedimentary environments often from the remains of microscopic organisms like radiolaria or through chemical replacement of limestone.

Uses & applications

Historically used for stone tools and arrowheads; currently used as decorative gravel, in lapidary work for cabochons and jewelry, and as a collector's specimen.

Geological facts

The reddish-brown color is typically caused by iron oxides like hematite. Jasper has been used since ancient times for cylinders and seals in Mesopotamia.

Field identification & locations

Identify in the field by its smooth, waxy texture and shell-like (conchoidal) fractures. It will easily scratch glass and cannot be scratched by a steel knife.