sedimentary

Chert (Jasper-like)

Silicon dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: tan, pink, and grayish-white; Luster: waxy to dull; Crystal structure: cryptocrystalline (microscopic quartz); Cleavage: none (conchoidal fracture); Specific gravity: 2.65.

Hardness: 7 on Mohs scale
Color: tan, pink, and grayish-white
Luster: waxy to dull

Identified July 9, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich microfossils or chemical precipitation in marine or groundwater environments. It typically occurs as nodules or beds within limestone or chalk formations.

Uses & applications

Historically used for making stone tools (arrowheads and scrapers) due to its sharp edges when fractured. Modernly used in landscaping, as an abrasive, and sometimes for lapidary work if highly colorful.

Geological facts

Chert is so hard it can strike sparks from steel, often used as 'flint' in historical firearms. It is incredibly chemically stable and can survive millions of years of erosion.

Field identification & locations

Identify in the field by its smooth, shell-like (conchoidal) fracture surfaces and its ability to scratch glass. Commonly found in riverbeds, glacial till, and limestone outcroppings.