sedimentary

Chert (Jasper/Flint variety)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale); Color: Olive green, brown, tan; Luster: Waxy to vitreous when wet; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.65

Hardness: 6
Color: Olive green, brown, tan
Luster: Waxy to vitreous when wet

Identified June 18, 2026More sedimentary →

Explore Chert (Jasper/Flint variety) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 6.5-7 (Mohs scale); Color: Olive green, brown, tan; Luster: Waxy to vitreous when wet; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.65

Formation & geological history

Formed from the accumulation of silica-rich organic remains (like radiolaria or diatoms) or chemical precipitation from groundwater within sedimentary beds. It can be found in formations ranging from Precambrian to Cenozoic ages.

Uses & applications

Historically used for stone tools (arrowheads/scrapers) due to its sharp edges; modern uses include lapidary work, jewelry (especially as jasper), and as an abrasive or construction aggregate.

Geological facts

Because of its conchoidal fracture, chert breaks into edges thinner than a steel scalpel. It is often referred to as 'flint' when found in chalk and 'jasper' when found in colorful, opaque forms.

Field identification & locations

Identify in the field by its hardness (it will scratch glass/steel) and its distinctive smooth, curved 'shell-like' fracture pattern. Common in river beds, beaches, and limestone outcrops.