sedimentary

Moqui Marble / Ironstone Concretion

Ironstone Concretion (Goethite/Hematite and Sandstone)

AI-generated identification · may be incorrect

Hardness: 5-6 (outer shell); Color: Dark brown to black outer, tan sand center; Luster: Dull or submetallic; Structure: Spheroidal/Concretionary; Specific Gravity: 3.5-5.0

Hardness: 5-6 (outer shell)
Color: Dark brown to black outer, tan sand center
Luster: Dull or submetallic

Identified May 22, 2026More sedimentary →

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Physical properties

Hardness: 5-6 (outer shell); Color: Dark brown to black outer, tan sand center; Luster: Dull or submetallic; Structure: Spheroidal/Concretionary; Specific Gravity: 3.5-5.0

Formation & geological history

Formed in the Jurassic period (approx. 150-190 million years ago) within layers of sandstone through the precipitation of iron-bearing minerals from groundwater.

Uses & applications

Geological study, metaphysical/collector interest, and decorative uses. They are also studied by NASA as analogs for 'blueberries' found on Mars.

Geological facts

Legend says ancestors of the Hopi tribe played games with them or used them to communicate with the deceased. They are often called 'shaman stones'.

Field identification & locations

Identified by their nearly perfect spherical or acorn shape and dark, hard iron-oxide crust. Commonly found in the Navajo Sandstone formations of Utah and Arizona.