sedimentary

Sandstone Moqui Marble (Concretion)

Iron oxide concretion (Hematite/Goethite and Quartz)

Hardness: 5.0-6.0 on Mohs scale; Color: Dark brown to rusty black exterior; Luster: Dull, earthy, or metallic; Structure: Spherical or ellipsoidal with a sandstone core; Specific Gravity: Approx 3.0-4.0.

Hardness: 5
Color: Dark brown to rusty black exterior
Luster: Dull, earthy, or metallic

Identified January 2, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in the Jurassic Navajo Sandstone roughly 130 to 180 million years ago. These concretions result from the precipitation of iron-rich minerals from groundwater flowing through porous sandstone, often forming around a nucleus.

Uses & applications

Primarily collected as geological specimens due to their unique shapes. In metaphysical circles, they are used as 'shaman stones.' Historically, they had no major industrial use but are significant for studying groundwater flow.

Geological facts

Legend has it that the spirits of the Hopi ancestors would play games with these 'marbles' at night. They are also being studied by NASA because similar 'blueberries' were found on Mars, suggesting past water activity.

Field identification & locations

Identify by the distinct spherical shape, dark iron-rich crust, and a lighter sandstone interior if broken. Often found in the American Southwest, particularly in Utah. Collectors should look for them weathering out of sandstone cliffs.

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