sedimentary

Flint

Microcrystalline Quartz (SiO2)

Hardness: 7 on the Mohs scale. Color: Typically gray, brown, yellowish-tan, or black. Luster: Waxy to vitreous. Crystal structure: Trigonal (microcrystalline/cryptocrystalline quartz known as chalcedony). Cleavage: None, exhibits conchoidal fracture. Specific gravity: 2.60 to 2.65.

Hardness: 7 on the Mohs scale
Color: Typically gray, brown, yellowish-tan, or black
Luster: Waxy to vitreous

Identified August 7, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed as nodules or masses in sedimentary rocks, predominantly chalk or limestone, through the replacement of calcium carbonate by silica-rich solutions over millions of years.

Uses & applications

Historically used for making stone tools, arrowheads, and firearm ignition (flintlock mechanisms). Also used in construction, abrasives, and sometimes decorative landscaping or knapping hobbies.

Geological facts

Flint and chert are essentially the same material, though 'flint' is traditionally used for the darker varieties found in chalk deposits. It was one of the earliest materials manipulated by early humans to create sharp cutting edges.

Field identification & locations

Identified easily in the field by its distinctive conchoidal fracture, waxy luster, and high hardness which easily scratches glass. Commonly found weathering out of chalk cliffs or limestone formations.