sedimentary

Chert (Jasper variety)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Tan/Brown/Black; Luster: Waxy to sub-vitreous; Crystal Structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6

Hardness: 6
Color: Tan/Brown/Black
Luster: Waxy to sub-vitreous

Identified March 21, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: Tan/Brown/Black; Luster: Waxy to sub-vitreous; Crystal Structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine or lacustrine environments. This specimen shows distinct banding/stratification, suggesting deposition in a sedimentary layer over millions of years.

Uses & applications

Commonly used for lapidary work (cabochons), historical tool-making (arrowheads/knives due to sharp edges), and as industrial abrasives.

Geological facts

Chert was one of the most important minerals for early humans, used for starting fires (flint) and making weapons. It is chemically identical to quartz but has a different microscopic structure.

Field identification & locations

Identify in the field by its smooth, waxy feel and shell-like (conchoidal) surface when broken. Commonly found in limestone or dolomite beds. It is very hard and will scratch glass easily.