sedimentary
Moqui Marble (Ironstone Concretion)
Iron Oxide Concretion (Fe2O3 / FeO(OH))
Hardness: 5-5.5 (Mohs scale); Color: Dark brown to black outer shell, yellow-tan sandstone interior; Luster: Dull/Earthy; Crystal Structure: Amorphous (shell); Specific Gravity: ~3.0-4.0
- Hardness
- 5-5
- Luster
- Dull/Earthy
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Physical properties
Hardness: 5-5.5 (Mohs scale); Color: Dark brown to black outer shell, yellow-tan sandstone interior; Luster: Dull/Earthy; Crystal Structure: Amorphous (shell); Specific Gravity: ~3.0-4.0
Formation & geological history
Formed through the precipitation of iron-rich groundwater flowing through porous sandstone. The iron minerals (hematite or goethite) cement sand grains together around a nucleus, often during the Jurassic period in the Navajo Sandstone formation.
Uses & applications
Predominantly used as a collector specimen, for geological study, and in metaphysical or spiritual practices. Small ones are occasionally used in craft jewelry.
Geological facts
Also known as 'Shaman Stones,' these often occur in pairs and are named after the Moqui (Hopi) Indians. They are famous for being terrestrial analogs to the 'blueberries' found on Mars by the Opportunity rover.
Field identification & locations
Identify in the field by their spherical or puck-like shape and unusually heavy weight relative to surrounding sandstone. They are commonly found in the deserts of Southern Utah and Arizona.
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