sedimentary

Chert (including varieties like Flint)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale); Color: White, tan, yellow, or grey (in this specimen); Luster: Waxy to dull; Crystal structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 (Mohs scale)
Color: White, tan, yellow, or grey (in this specimen)
Luster: Waxy to dull

Identified March 26, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by the precipitation of silica from groundwater or within maritime sediments. Often found as nodules in limestone or chalk beds. Most specimens date from the Paleozoic or Mesozoic eras.

Uses & applications

Historically used for stone tools (arrowheads, knives) due to its sharp conchoidal fracture. Modern uses include road surfacing, jewelry (as jasper/agate), and fire-starting flint.

Geological facts

Chert is so hard it can scratch glass and steel. It was one of the most vital resources for prehistoric humans, allowing for the creation of durable, razor-sharp edges.

Field identification & locations

Identify in the field by its smooth, shell-like (conchoidal) fracture and its ability to spark against steel. Commonly found in creek beds or eroding out of limestone cliffs.