sedimentary
Moqui Marble
Iron Oxide Concretion (Limonite/Hematite over Sandstone)
Hardness: 5.0 - 5.5 on Mohs scale (outer shell); Color: Brown to dark black exterior with tan interior; Luster: Dull, earthy; Crystal structure: Amorphous; Cleavage: None; Specific gravity: 3.5 - 4.5.
- Hardness
- 5
- Color
- Brown to dark black exterior with tan interior
- Luster
- Dull, earthy
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Physical properties
Hardness: 5.0 - 5.5 on Mohs scale (outer shell); Color: Brown to dark black exterior with tan interior; Luster: Dull, earthy; Crystal structure: Amorphous; Cleavage: None; Specific gravity: 3.5 - 4.5.
Formation & geological history
Formed roughly 25 million to 300,000 years ago via groundwater precipitation. They form when iron-rich minerals precipitate in the pore spaces between sand grains in host sandstone (predominantly the Navajo Sandstone formation).
Uses & applications
Predominantly used as collectible geological specimens and in metaphysical practices as 'balancing stones.' Also used as a curriculum aid for teaching about groundwater chemistry and Martian geology.
Geological facts
They are terrestrial analogues to the 'Blueberries' found on Mars by the Opportunity rover. The name 'Moqui' comes from the Hopi tribe (formerly referred to as the Moqui people), whose folklore suggests ancestors played games with the marbles.
Field identification & locations
Identify in the field by their spherical or blueberry-like shape emerging from sandstone cliffs or scattered on desert floors. Primarily found in the Grand Staircase-Escalante National Monument in southern Utah. Note: Collecting is strictly illegal within National Parks/Monuments.
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