sedimentary

Chert (Flint)

Microcrystalline Quartz (SiO2)

Mohs Hardness: 7; Color: Dark grey to black with light banding; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7
Color: Dark grey to black with light banding
Luster: Waxy to vitreous

Identified May 12, 2026More sedimentary →

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Physical properties

Mohs Hardness: 7; Color: Dark grey to black with light banding; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed from the accumulation of siliceous remains of marine organisms or through chemical precipitation in limestone or chalk deposits. Commonly found in sedimentary basins worldwide.

Uses & applications

Historically used for stone tools and starting fires; currently used as construction aggregate, road base, and for lapidary jewelry.

Geological facts

Flint was arguably the most important mineral for early human technology because it can be knapped into razor-sharp edges. It is often found as nodules within limestone or chalk beds.

Field identification & locations

Identify by its conchoidal (shell-like) fracture pattern, waxy texture, and its ability to scratch glass easily. Commonly found in riverbeds or coastal chalk cliffs.