sedimentary

Chert (specifically Flint or Jasper variant)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Dark brown to black with banding; Luster: Waxy to dull; Crystal structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 on Mohs scale
Color: Dark brown to black with banding
Luster: Waxy to dull

Identified March 16, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Dark brown to black with banding; Luster: Waxy to dull; Crystal structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed through the accumulation of siliceous remains of organisms (like diatoms or radiolarians) or chemical precipitation from silica-rich fluids in sedimentary basins. Specimens can range from Precambrian to Recent geological ages.

Uses & applications

Historically used for stone tools (arrowheads/scrapers) and fire-starting. Currently used as an abrasive, in construction aggregate, and as a semi-precious gemstone for jewelry (cabochons) or decorative carvings.

Geological facts

Chert was one of the first materials utilized by early humans for tool-making because of its predictable conchoidal fracture which creates razor-sharp edges. Gunflint was a critical industrial supply for flintlock firearms for centuries.

Field identification & locations

Identify in the field by its smooth, shell-like (conchoidal) fracture surfaces and its ability to scratch glass. It is commonly found as nodules in limestone or chalk beds. Collectors look for unique banding patterns or colors.