sedimentary

Chert (Jasper/Flint variety)

Microcrystalline Quartz (SiO2)

Hardness: 7 on Mohs scale; Color: Variable (grey, white, brown, with orange/red iron staining); Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Hardness: 7 on Mohs scale
Color: Variable (grey, white, brown, with orange/red iron staining)
Luster: Waxy to vitreous

Identified March 25, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or by chemical precipitation from silica-rich fluids. Often found in limestone or dolomite beds. Geological age ranges from Precambrian to Holocene.

Uses & applications

Historically used for stone tools (knapping) due to its sharp edges. Currently used in road construction, landscape decoration, and occasionally as semi-precious gemstones (Jasper) for jewelry.

Geological facts

Chert was one of the most important materials in human prehistory for creating arrowheads and scrapers. The reddish-orange staining in this specimen is likely due to iron oxide impurities (Hematite or Goethite).

Field identification & locations

Identify in the field by its characteristic smooth, curved 'conchoidal' fractures and its ability to scratch glass. It is common in regions with sedimentary bedrock like Ohio, Missouri, and Texas. Collectors look for unique banding or vivid colors.

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