sedimentary

Chert with Jasper and Quartz

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 Mohs; Color: Reddish-brown, white, and translucent blue-grey; Luster: Vitreous to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture)

Hardness: 7 Mohs
Color: Reddish-brown, white, and translucent blue-grey
Luster: Vitreous to waxy

Identified June 15, 2026More sedimentary →

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Physical properties

Hardness: 7 Mohs; Color: Reddish-brown, white, and translucent blue-grey; Luster: Vitreous to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture)

Formation & geological history

Formed from the accumulation of silica-rich fluids in limestone or volcanic ash beds. This specimen displays a mix of jasper (red from iron inclusions) and common opal or translucent chalcedony.

Uses & applications

Historically used for stone tools and arrowheads. Currently used for lapidary work, cabochons, and as a collector's specimen.

Geological facts

This specimen shows 'brecciation' or mixing where different pulses of silica saturated water filled cavities, creating the distinct color zones. Chert is one of the most durable sedimentary rocks.

Field identification & locations

Identify by its hardness (will scratch glass) and smooth, shell-like (conchoidal) fracture surfaces. Commonly found in river beds or eroaded sedimentary basins.