sedimentary

Chert (Jasper/Agate mix)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale; Color: Brown, tan, and waxy grey; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).

Hardness: 6
Color: Brown, tan, and waxy grey
Luster: Waxy to dull

Identified July 1, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Brown, tan, and waxy grey; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).

Formation & geological history

Formed through the accumulation of silica-rich fluids in limestone or volcanic cavities, where the silica precipitate hardens over millions of years. This specimen shows a mix of opaque jasper and translucent agate layers.

Uses & applications

Used historically for stone tools due to its sharp edges; currently used for lapidary work, decorative landscaping, and as collector specimens.

Geological facts

Chert has been used since the Stone Age to make arrowheads and spear points. The waxy, translucent portions in this specimen are technically chalcedony/agate.

Field identification & locations

Identify in the field by its waxy appearance and conchoidal (shell-like) fracture patterns. Frequently found in riverbeds, gravel pits, and sedimentary rock outcrops globally.