sedimentary

Moqui Marble (Iron-Oxide Concretion)

Iron Oxide Concretion (Fe2O3)

Hardness: 5-5.5 on Mohs scale. Color: Brownish-red to black exterior, sand-colored interior. Luster: Dull/Earthy. Structure: Spherical to subspherical mass. Cleavage: None (fractures irregularly). Specific Gravity: 3.5 - 4.2.

Hardness: 5-5
Color: Brownish-red to black exterior, sand-colored interior
Luster: Dull/Earthy

Identified March 27, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the precipitation of iron-bearing minerals (hematite and goethite) around a nucleus within porous sandstone layers. These specific forms are primarily associated with the Navajo Sandstone of the Jurassic period (approx. 180 million years ago).

Uses & applications

Primarily used as metaphysical stones, educational geological specimens, and decorative collectibles. Historically used by Native American tribes for games and as sacred objects.

Geological facts

Also known as 'Shaman Stones,' these concretions are often found in pairs. Research suggests they may have formed similarly to the 'blueberries' (hematite spherules) found on the surface of Mars by the Opportunity rover.

Field identification & locations

Identify by their distinct spherical shape and dark, iron-rich outer shell. Common in the American Southwest (Utah/Arizona). To identify in the field, look for dark round balls weathering out of light-colored sandstone cliffs or littering valley floors.

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