sedimentary
Ironstone Concretion (Moqui Marble)
Iron-oxide Concretion (Hydrated ferric oxide, Fe2O3·nH2O)
Hardness: 5-5.5 (Mohs scale), Color: Rusty brown to dark chocolate, Luster: Dull/Earthy, Crystal Structure: Amorphous or nanocrystalline crust, Specific Gravity: 3.2-4.2
- Hardness
- 5-5
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Physical properties
Hardness: 5-5.5 (Mohs scale), Color: Rusty brown to dark chocolate, Luster: Dull/Earthy, Crystal Structure: Amorphous or nanocrystalline crust, Specific Gravity: 3.2-4.2
Formation & geological history
Formed through precipitation of iron-rich minerals around a nucleus (like a sand grain) within porous sedimentary rock. Often linked to ancient groundwater movement through sandstone layers like the Navajo Sandstone during the Jurassic period.
Uses & applications
Primarily used as geological specimens for collecting, education, and metaphysical 'shaman stones'. Historically explored for iron content, though not an efficient modern ore source.
Geological facts
Commonly called 'Moqui Marbles,' these specimens can range from the size of a pea to a baseball. They are often found in pairs and have been used in indigenous folklore for rituals and games.
Field identification & locations
Identify in the field by their spherical shape and dark, hard iron-rich 'shell' that contrasts with the softer, lighter-colored host sandstone. Frequently found in the American Southwest, specifically Utah and Arizona.
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