sedimentary

Chert (varieties include Flint and Jasper)

Silicon Dioxide (SiO2) - Microcrystalline Quartz

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: typically grey, brown, or tan (as seen in the specimen); Luster: waxy to dull; Structure: microcrystalline (no visible grains); Cleavage: none, exhibits distinct conchoidal fracture; Specific gravity: 2.65.

Hardness: 7 on Mohs scale
Color: typically grey, brown, or tan (as seen in the specimen)
Luster: waxy to dull

Identified March 8, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich biogenic remains (like diatoms or radiolaria) or chemical precipitation in marine environments and limestone cavities. It can range from precambrian to recent geological ages.

Uses & applications

Historically used for stone tools (arrowheads, knives) due to its sharp edges; modern uses include road surfacing, jewelry (as jasper/agate), and as a strike-stone for fire-starting.

Geological facts

Chert was one of the most important minerals to prehistoric humans; its ability to break into razor-sharp edges made it essential for survival. It is so tough it can spark when struck against steel.

Field identification & locations

Identify in the field by its hardness (it will scratch glass) and its smooth, curved 'shell-like' (conchoidal) fracture surfaces. Commonly found as nodules or layers within limestone or chalk formations.