sedimentary

Chert (Jasper)

Cryptocrystalline Quartz (SiO2)

Hardness: 6.5-7 on the Mohs scale. Color: Green and reddish-brown mottling. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific Gravity: 2.6-2.7.

Hardness: 6
Color: Green and reddish-brown mottling
Luster: Waxy to vitreous

Identified February 27, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from the accumulation of microscopic silica organisms (radiolarians/diatoms) or through the replacement of limestone. This specimen likely has iron impurities (hematite) giving it the reddish hues. Geological age can range from Precambrian to Cenozoic.

Uses & applications

Historically used for stone tools (knapping) due to its sharp conchoidal fracture. Modern uses include semi-precious jewelry (cabochons), lapidary art, and aquarium gravel.

Geological facts

Jasper is often referred to as 'spotted or speckled stone.' It was one of the first materials used by early humans to create arrowheads and scrapers because it is harder than steel and breaks into razor-sharp edges.

Field identification & locations

Identify in the field by its smooth, waxy texture and sharp, shell-like (conchoidal) breakage patterns. It cannot be scratched by a steel knife. Commonly found in riverbeds, glacial deposits, and sedimentary formations globally.

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