sedimentary

Chert (Jasper)

Microcrystalline Quartz (SiO2)

Hardness: 7 on Mohs scale; Color: Reddish-brown, tan, and cream; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Reddish-brown, tan, and cream
Luster: Dull to waxy

Identified March 18, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Reddish-brown, tan, and cream; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in sedimentary environments. Common in marine limestone formations, dating from the Precambrian to Cenozoic eras.

Uses & applications

Historically used for making sharp tools and arrowheads; currently used as decorative gravel, in lapidary work for jewelry (cabochons), and for flint-striking kits.

Geological facts

This specimen displays the characteristic waxy luster and conchoidal 'shell-like' fracture pattern once prized by early humans for toolmaking. Variations with hematite inclusions are specifically called Jasper.

Field identification & locations

Identify in the field by its smooth, glass-like fracture and the fact that it will easily scratch glass. Usually found in stream beds, gravel pits, or within limestone outcrops. Collectors look for unique banding or patterns.