sedimentary

Chert (Grey-Green Var.)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs); Color: Greyish-green; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (Conchoidal fracture); Specific gravity: 2.65

Hardness: 6
Color: Greyish-green
Luster: Waxy to dull

Identified June 25, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs); Color: Greyish-green; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (Conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed as nodules or layered deposits through the accumulation of silica-rich microfossils or chemical precipitation in marine environments; age varies from Precambrian to Cenozoic.

Uses & applications

Used historically for tools and weapons due to its sharp edges; industrially for abrasives or as a component in construction aggregate; and as a lapidary material for polishing.

Geological facts

Chert was a primary material used by prehistoric humans to create spearheads and knives. It is essentially a variety of microcrystalline quartz.

Field identification & locations

Identify by its waxy luster, hardness (it scratches glass), and characteristic curved seashell-like fractures. Frequently found in limestone and dolomite formations.