sedimentary

Chert / Jasper

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Tan, brownish-gray, pinkish-orange, buff; Luster: Waxy to vitreous, dull weathered exterior; Cleavage: None (conchoidal fracture); Specific gravity: ~2.65

Hardness: 6
Color: Tan, brownish-gray, pinkish-orange, buff
Luster: Waxy to vitreous, dull weathered exterior

Identified July 25, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Tan, brownish-gray, pinkish-orange, buff; Luster: Waxy to vitreous, dull weathered exterior; Cleavage: None (conchoidal fracture); Specific gravity: ~2.65

Formation & geological history

Formed via precipitation of silica-rich fluids in sedimentary layers or within cavities of volcanic/limestone formations. Fine microcrystalline structure grows as micro-fibrous chalcedony silica.

Uses & applications

Historically used for knapping sharp stone tools like arrowheads and scrapers. Modern uses include decorative rock garden specimens, lapidary cabochons, and landscape stone.

Geological facts

Chert and jasper are among the oldest materials used by early humans for tools due to their predictable conchoidal fracturing which yields razor-sharp edges.

Field identification & locations

Identified in the field by its distinct smooth conchoidal fracture surfaces alongside a dull, weathered chalky rind (cortex) and high hardness (scratches steel). Common in sedimentary basins worldwide.