sedimentary

Limonite-stained Chert/Jasper

Microcrystalline Quartz (SiO2) with Iron Oxides (FeO(OH)·nH2O)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale. Color: Rusty brown, orange, and ochre with hints of green or tan. Luster: Dull to waxy. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.6-2.7.

Hardness: 6
Color: Rusty brown, orange, and ochre with hints of green or tan
Luster: Dull to waxy

Identified May 18, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed via the accumulation of silica-rich microfossils (like radiolaria) or chemical precipitation in marine environments. The rusty coloring is due to secondary weathering and the infiltration of iron-rich groundwater (limonitization) over millions of years.

Uses & applications

Used historically for tool making (flint knapping). Today, it is used for landscaping, as a lapidary material for cabochons if the core is solid, and as a common collectible for rockhounds.

Geological facts

This specimen displays a heavy weathering rind. Iron oxides like limonite are actually a mixture of hydrous iron oxides and are a common cause of the 'rusty' appearance in sedimentary rocks.

Field identification & locations

Identified in the field by its hardness (it will scratch glass), its heavy weight relative to its size, and the characteristic orange-brown oxidation. Found globally in riverbeds, glacial tills, and sedimentary basins.