sedimentary

Moqui Marble (Ironstone Concretion)

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

AI-generated identification · may be incorrect

Hardness: 5-6 (outer shell); Color: Rusty brown, dark chocolate brown, to black; Luster: Dull, earthy; Structure: Spherical or disc-like concretion; Specific Gravity: 3.4-5.0

Hardness: 5-6 (outer shell)
Color: Rusty brown, dark chocolate brown, to black
Luster: Dull, earthy

Identified June 7, 2026More sedimentary →

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Physical properties

Hardness: 5-6 (outer shell); Color: Rusty brown, dark chocolate brown, to black; Luster: Dull, earthy; Structure: Spherical or disc-like concretion; Specific Gravity: 3.4-5.0

Formation & geological history

Formed by the precipitation of iron oxide minerals around a nucleus (often sand) within groundwater-soaked sedimentary layers, primarily the Navajo Sandstone. They are roughly 25 to 190 million years old.

Uses & applications

Geological collecting, metaphysical use (energy stones), and planetary research (analogues for 'blueberries' on Mars).

Geological facts

The name 'Moqui' comes from the Hopi tribe. NASA scientists study these because similar hematite spherules were found on Mars by the Opportunity rover, suggesting a watery past for the red planet.

Field identification & locations

Identified by their nearly perfect spherical or button shape and heavy iron-rich weight. Commonly found in the American Southwest (Utah/Arizona), they often weather out of sandstone cliffs.