sedimentary

Chert (or Jasper)

Microcrystalline Quartz (SiO2)

Hardness: 7 Mohs scale; Color: Cream, tan, and reddish-orange (iron-stained); Luster: Waxy to dull; Crystal structure: Trigonal/Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 Mohs scale
Color: Cream, tan, and reddish-orange (iron-stained)
Luster: Waxy to dull

Identified June 2, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by the precipitation of silica from groundwater or as a replaces of biological materials like limestone/chalk. Often found in nodules within sedimentary rock beds; age varies from Precambrian to Cenozoic.

Uses & applications

Historically used for stone tools (arrowheads). Modern uses include landscaping, as a construction aggregate, and occasionally as semi-precious gemstones in jewelry (when decorative like jasper).

Geological facts

Chert has been used by humans for millions of years to create sharp-edged tools because of its conchoidal fracture pattern, which produces edges sharper than a steel scalpel.

Field identification & locations

Identify by its smooth, waxy surface and the way it breaks into curved, shell-like flakes. It will easily scratch glass and cannot be scratched by a steel knife. Found globally in limestone areas.