sedimentary

Chert (Pink Jasper/Agate variety)

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 (Mohs); Color: Mottled pink, white, and tan with dark manganese or iron inclusions; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

Hardness: 6
Luster: Waxy to dull

Identified March 25, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich microfossils (like radiolarians) or the chemical precipitation of silica in groundwater within sedimentary basins. The pink hue indicates trace amounts of iron oxides.

Uses & applications

Used primarily for lapidary work (cabs and tumbled stones), aquarium décor, and historically as a raw material for stone tools due to its sharp conchoidal fracturing.

Geological facts

Because of its high hardness and silica content, this rock type was one of the most important materials for early humans to create arrowheads and scrapers. The dark dendritic patterns often seen in specimens like this are manganese oxide 'ferns'.

Field identification & locations

Identify in the field by its waxy texture and sharp, shell-like (conchoidal) edges when broken. It will scratch steel and glass. Commonly found in riverbeds or as nodules within limestone formations globally.

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