sedimentary

Chert / Jasper

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale. Color: Mottled red, orange, tan, and black due to iron oxides and manganese. Luster: Waxy to dull. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture).

Hardness: 6
Luster: Waxy to dull

Identified March 25, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich microfossils (like radiolaria or diatoms) or by the chemical precipitation of silica in marine environments. Often found in nodules within limestone or as bedded deposits.

Uses & applications

Historically used for stone tools (arrowheads and scrapers) due to its sharp edges. Currently used for lapidary work, jewelry (cabochons), and as landscaping rock.

Geological facts

Because of its extreme hardness and conchoidal fracture, it was the primary material for prehistoric 'flint knapping.' The red variety is specifically referred to as Jasper.

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 or coastal cliffs where sedimentary layers are exposed.