sedimentary

Chert / Jasper

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5–7 on Mohs scale. Color: Greenish-brown, tan, and earthy tones. Luster: Waxy to dull. Crystal Structure: Trigonal (microcrystalline/cryptocrystalline). Cleavage: None (conchoidal fracture).

Hardness: 6
Color: Greenish-brown, tan, and earthy tones
Luster: Waxy to dull

Identified April 12, 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 the chemical replacement of limestone/dolomite by silica-rich fluids. Can be of various geological ages from Precambrian to Cenozoic.

Uses & applications

Historically used for stone tools (arrowheads/scrapers) due to its sharp fracture edges. Today used as aquarium gravel, landscaping stone, and occasionally in lapidary work for cabochons.

Geological facts

Chert is so durable that it often survives long after the surrounding rock has weathered away. Jasper is the name specifically given to opaque, impure varieties of chert often colored by iron oxides.

Field identification & locations

Identify in the field by its hardness (it should scratch glass), its waxy feel, and its curved, shell-like (conchoidal) fracture surfaces. Commonly found in riverbeds, glacial till, and embedded in limestone outcrops.