sedimentary

Chert (White Variety)

Silicon Dioxide (SiO2)

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

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

Identified April 5, 2026More sedimentary →

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Physical properties

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

Formation & geological history

Formed as a chemical precipitate in marine environments or through the replacement of limestone. It consists of microscopic quartz crystals that accumulate on the ocean floor, often from the silica-rich remains of organisms like diatoms and radiolarians.

Uses & applications

Historically used for stone tools (arrowheads, scrapers) due to its sharp edges when broken. Today, it is used as road surfacing material and occasionally in construction as a sturdy aggregate.

Geological facts

Chert is so hard it can spark when struck against steel, leading to its historical use as 'firestone' or flint. This specific white, weathered variety is sometimes referred to as 'Novaculite' in certain regions like Arkansas.

Field identification & locations

Identify in the field by its extreme hardness (cannot be scratched by a steel knife) and its smooth, curved conchoidal fractures. It is commonly found as nodules or layers within limestone or dolomite beds.