sedimentary

Chert (Jasper variation)

Silicon dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown to tan; Luster: Waxy to dull; Crystal structure: Cryptocrystalline (Microcrystalline quartz); Cleavage: None (Conchoidal fracture); Specific gravity: 2.58-2.91

Hardness: 6
Color: Reddish-brown to tan
Luster: Waxy to dull

Identified May 13, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by the accumulation of siliceous remains of organisms or chemical precipitation from silica-rich fluids. Common in sedimentary sequences such as limestone or shale beds across many geological eras.

Uses & applications

Historical use for stone tools/weapons; modern use in landscaping, aggregate, and occasionally semi-precious jewelry or lapidary art.

Geological facts

Chert was one of the most important minerals for early humans because its conchoidal fracture produces extremely sharp edges, ideal for arrowheads and scrapers.

Field identification & locations

Identify in the field by its hardness (scratches glass), waxy luster, and shell-like (conchoidal) fracture surfaces. Commonly found in nodules or beds within sedimentary rock layers.