sedimentary

Chert (Mookaite style Jasper)

Microcrystalline Quartz (SiO2) with Hematite/Goethite inclusions

Hardness: 6.5-7 on Mohs scale. Color: Reddish-maroon and cream/white bands. Lustre: Vitreous to waxy. Crystal Structure: Trigonal (microcrystalline). Fracture: Conchoidal. Opaque to translucent edges.

Hardness: 6
Color: Reddish-maroon and cream/white bands

Identified June 27, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from the accumulation of silica-rich skeletal remains of radiolaria. The colors come from iron oxide minerals leaching into the silica during formation. Commonly found in sedimentary basins or as nodules in limestone.

Uses & applications

Used primarily for lapidary work (jewelry, cabochons, beads) and as a decorative stone. Historically used for making sharp tools like arrowheads and scrapers due to its conchoidal fracture.

Geological facts

This specimen shows banding characteristic of some 'Jaspers'. While often called Jasper in the gem trade, geologically it is a variety of chert. It is exceptionally durable and resists weathering better than common surrounding rocks.

Field identification & locations

Identify in the field by its smooth, shell-like (conchoidal) fracture surfaces and its inability to be scratched by a steel knife. It is often found as smooth river pebbles or within sedimentary strata.

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