sedimentary

Limonite Geode / Ironstone Concretion with Quartz

Limonite with Quartz (FeO(OH)·nH2O + SiO2)

AI-generated identification · may be incorrect

Hardness: 4-5.5 (limonite shell), 7 (quartz crystals); Color: Dark brown to ochre; Luster: Dull/earthy exterior, vitreous interior; Crystal structure: Amorphous shell, trigonal quartz crystals inside.

Hardness: 4-5
Color: Dark brown to ochre
Luster: Dull/earthy exterior, vitreous interior

Identified June 19, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed via the precipitation of iron oxides from groundwater within sedimentary layers, often creating a hollow concretion which later hosts secondary mineral growth like quartz.

Uses & applications

Geological collecting, educational specimens, and occasionally as a minor iron ore.

Geological facts

These are often called 'rattle stones' or 'etites' if the internal crystals break loose and shake inside the hollow cavity.

Field identification & locations

Identified by its heavy iron-rich outer shell and characteristic vugs or hollows often filled with small crystals. Commonly found in areas with iron-rich sandstone or clay deposits.