sedimentary

Chert (Jasper)

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 Mohs; Color: Opaque reddish-orange, tan, and brown; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 6
Color: Opaque reddish-orange, tan, and brown
Luster: Waxy to dull

Identified July 19, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Opaque reddish-orange, tan, and brown; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed primarily through the replacement of limestone or carbonate rocks by silica-rich fluids. It can also form from the accumulation of siliceous remains of marine organisms like diatoms and radiolarians.

Uses & applications

Historically used for making stone tools (arrowheads, scrapers) due to conchoidal fracture. Modernly used in lapidary work, jewelry (especially when patterned as Jasper), and as decorative landscaping stone.

Geological facts

This specimen displays the characteristically sharp, scalloped edges resulting from conchoidal fracture, which made this material the primary resource for prehistoric toolmaking. Jasper is essentially chert that is colored by iron impurities.

Field identification & locations

Identify in the field by its hardness (it will scratch glass), its waxy feel, and the distinctive way it chips (conchoidal fracture). Common in riverbeds and limestone outcrops throughout North America and Europe.