sedimentary
Moqui Marble (Sandstone Concretion)
Hematite-cemented Sandstone (Fe2O3 + SiO2)
Hardness: 5-7 (shell) / 2-3 (core); Color: dark brown to black exterior, tan interior; Luster: dull to sub-metallic; Structure: spherical to disc-like; Cleavage: none; SG: 2.5-3.5
- Hardness
- 5-7 (shell) / 2-3 (core)
- Color
- dark brown to black exterior, tan interior
- Luster
- dull to sub-metallic
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Physical properties
Hardness: 5-7 (shell) / 2-3 (core); Color: dark brown to black exterior, tan interior; Luster: dull to sub-metallic; Structure: spherical to disc-like; Cleavage: none; SG: 2.5-3.5
Formation & geological history
Formed in the Navajo Sandstone formation during the Jurassic period. Groundwater rich in iron minerals precipitated around a nucleus, creating a hard iron-oxide shell around a softer sand core.
Uses & applications
Geological collecting, metaphysical use (spirit stones), and scientific study for planetary analogs (analogs for 'blueberries' found on Mars).
Geological facts
The name 'Moqui' comes from the Hopi Tribe's former name. They are also known as Shaman stones and are protected by law in many areas, such as U.S. National Parks.
Field identification & locations
Identify by the distinct dark, rusty-brown iron shell and spherical shape, often found clustered in desert sandstone flats or weathering out of canyon walls.
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