sedimentary

Flint (or Chert)

Silicon dioxide (SiO2) microcrystalline quartz

Hardness: 7 on the Mohs scale. Color ranges from grey, brown, black to white, often with banded or mottled patterns. Luster: Vitreous to waxy. Crystal structure: Microcrystalline/cryptocrystalline (chalcedony). Cleavage: None, exhibits characteristic conchoidal fracture. Specific gravity: 2.60 to 2.65.

Hardness: 7 on the Mohs scale
Luster: Vitreous to waxy

Identified August 6, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the replacement of calcium carbonate by silica-rich solutions in sedimentary environments, typically within chalk or limestone formations over millions of years.

Uses & applications

Historically used for making stone tools, arrowheads, and striking fire (when hit against steel). Also used in decorative landscaping, road construction, and previously in flintlock firearms.

Geological facts

Flint is extremely durable and breaks with sharp edges, making it a primary material for prehistoric stone tool technology. It has been utilized by humans for hundreds of thousands of years.

Field identification & locations

Easily identified in the field by its smooth, waxy luster, conchoidal fracture (curved, shell-like breaking pattern), and high hardness that easily scratches glass. Commonly found as nodules within chalk and limestone deposits worldwide.

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