sedimentary

Moqui Marble

Ironstone Concretion (Ferruginous sandstone)

AI-generated identification · may be incorrect

Hardness: 5-5.5 (interior) to 6 (exterior), Color: chocolate brown to black, Luster: dull to earthy, Structure: spherical/sub-spherical concretion with a sandstone core and hematite shell.

Hardness: 5-5

Identified July 1, 2026More sedimentary →

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Physical properties

Hardness: 5-5.5 (interior) to 6 (exterior), Color: chocolate brown to black, Luster: dull to earthy, Structure: spherical/sub-spherical concretion with a sandstone core and hematite shell.

Formation & geological history

Formed in the Jurassic Navajo Sandstone roughly 130 to 180 million years ago. They are created by the precipitation of hematite and goethite within the sandstone matrix from groundwater.

Uses & applications

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

Geological facts

Small sphere-shaped hematite concretions similar to these were discovered on Mars by the Opportunity rover in 2004, indicating past water was once present on the Red Planet.

Field identification & locations

Identified by their dark brown color and heavy weight relative to size. Found primarily in the American Southwest (Utah/Arizona). Note that collecting is prohibited in many National Parks.