sedimentary

Moqui Marble

Iron Oxide Concretion (Limonite/Hematite shell with Sandstone core)

AI-generated identification · may be incorrect

Hardness: 5-5.5 (shell), 2-3 (core); Color: Dark brown to black exterior, tan/sandy interior; Luster: Dull or sub-metallic; Crystal structure: Amorphous/microcrystalline; Specific Gravity: 3.5-4.5 (exterior).

Hardness: 5-5
Color: Dark brown to black exterior, tan/sandy interior
Luster: Dull or sub-metallic

Identified April 19, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed roughly 25 million years ago within the Navajo Sandstone via groundwater precipitation. Dissolved iron minerals gathered around a nucleus, creating a hard rind over a soft sandstone interior.

Uses & applications

Primarily used as a collector specimen, in spiritual/metaphysical practices, and for geological study.

Geological facts

They are named after the Hopi tribe, formerly called the 'Moqui.' They are often referred to as 'Earth's blueberries' because similar iron concretions (nicknamed blueberries) were discovered on Mars by the Opportunity rover, suggesting a shared geological water history.

Field identification & locations

Identify by their spherical or puck-like shape, heavy weight for their size, and rough, dark exterior. Most commonly found in the Grand Staircase-Escalante National Monument in southern Utah.