sedimentary
Moqui Marble / Ironstone Concretion
Ironstone Concretion (Goethite/Hematite and Sandstone)
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
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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.
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