sedimentary

Moqui Marble (Ironstone Concretion)

Goethite/Hematite Concretion (Fe2O3 / FeO(OH))

AI-generated identification · may be incorrect

Hardness: 5-5.5 (outer shell), 3-4 (inner core). Color: Dark brown, rusty orange, or tan. Luster: Dull/Earthy to sub-metallic. Crystal structure: Amorphous or microcrystalline shell around a sandstone center.

Hardness: 5-5
Color: Dark brown, rusty orange, or tan
Luster: Dull/Earthy to sub-metallic

Identified March 22, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed during the Jurassic period (approx. 190 million years ago) via groundwater precipitation. Iron minerals dissolved in water precipitated around a nucleus within porous sandstone, eventually forming a hardened shell.

Uses & applications

Primarily collected as geological curiosities, used in metaphysical practices ('shaman stones'), and studied by NASA as terrestrial analogs to 'blueberries' found on Mars.

Geological facts

They are named after the Hopi Tribe (formerly 'Moqui'). On Mars, the Opportunity rover found near-identical structures composed of hematite, suggesting that liquid water once existed on the Red Planet.

Field identification & locations

Identified by their round/ellipsoidal shape, heavy weight for their size, and distinct dark iron-rich crust. Found primarily in the Navajo Sandstone of Utah and Arizona. Collectors should look for weathered outcrops.