sedimentary

Chert (Jasper)

Microcrystalline Quartz (SiO2)

Hardness: 6.5 - 7 on Mohs scale. Color: Reddish-pink with banding. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.6 - 2.7.

Hardness: 6
Color: Reddish-pink with banding
Luster: Waxy to vitreous

Identified April 6, 2026More sedimentary →

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Physical properties

Hardness: 6.5 - 7 on Mohs scale. Color: Reddish-pink with banding. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.6 - 2.7.

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like radiolarians or diatoms) or by chemical precipitation in saltwater and groundwater environments. This specimen shows a waxy luster typical of microcrystalline silicates.

Uses & applications

Historically used for stone tools/arrowheads. Modernly used in lapidary work for jewelry (cabochons), or as decoration in landscaping and aquariums.

Geological facts

Red chert is often called Jasper if it is opaque and rich in iron oxides. It has been used by humans for hundreds of thousands of years to create sharp-edged tools due to its predictable conchoidal fracture pattern.

Field identification & locations

Identify by its 'shell-like' conchoidal fractures, waxy texture, and inability to be scratched by a steel knife. Commonly found in riverbeds or as nodules within limestone or chalk formations.