sedimentary

Chert (Jasper/Flint variety)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 Mohs scale; Color: Brown, tan, reddish tones; Luster: Waxy to vitreous; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6

Hardness: 7 Mohs scale
Color: Brown, tan, reddish tones
Luster: Waxy to vitreous

Identified May 29, 2026More sedimentary →

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Physical properties

Hardness: 7 Mohs scale; Color: Brown, tan, reddish tones; Luster: Waxy to vitreous; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6

Formation & geological history

Formed as nodules or layered deposits when microcrystalline quartz precipitates from watery solutions. It is common in limestone or chalk beds and can range from Precambrian to recent geological ages.

Uses & applications

Used historically for stone tools and arrowheads due to its sharp edges; used today as decorative stones, in lapidary work (jewelry), and for starting fires (flint).

Geological facts

Chert was one of the first materials used by early humans to create sophisticated tools. Because it breaks with conchoidal fractures, it creates edges sharper than a steel scalpel.

Field identification & locations

Identify in the field by its very smooth surface, waxy luster, and petal-shaped (conchoidal) chips or fractures. It can scratch glass and steel. Common globally in sedimentary rock outcrops.