sedimentary

Chert / Flint

Microcrystalline Quartz (SiO2)

Hardness: 7 on Mohs scale; Color: Gray, tan, brown, or black with waxy luster; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Hardness: 7 on Mohs scale
Color: Gray, tan, brown, or black with waxy luster

Identified June 25, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Gray, tan, brown, or black with waxy luster; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Formation & geological history

Formed by the accumulation of siliceous remains of organisms or chemical precipitation from groundwater within sedimentary layers like limestone. Found in strata ranging from Precambrian to recent.

Uses & applications

Historically used for stone tools and weapons (arrowheads); used industrially in road surfacing and as a raw material for ceramics and glass.

Geological facts

Chert and flint were arguably the most important materials for early human technology because of their ability to break into razor-sharp edges through conchoidal fracturing.