sedimentary

Chert (White Chert or Flint)

Microcrystalline or cryptocrystalline quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: White to light gray; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: White to light gray
Luster: Dull to waxy

Identified February 21, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: White to light gray; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like radiolaria or diatoms) or chemical precipitation from groundwater within limestone or chalk beds. It can date from the Precambrian to Holocene.

Uses & applications

Historically used for stone tools (knapping) and fire-starting. Currently used as road surfacing, concrete aggregate, and sometimes as a minor gemstone for lapidary work.

Geological facts

Because of its extreme hardness and conchoidal fracture, it produces edges sharper than a steel scalpel. Native Americans and other ancient cultures used white chert extensively for arrowheads and scrapers.

Field identification & locations

Identify in the field by its waxy appearance, extreme hardness (it will scratch glass and steel), and curved, shell-like (conchoidal) fracture patterns. Frequently found in riverbeds or eroding out of limestone outcrops.