sedimentary

Ironstone Concretion (Moqui Marble)

Iron-oxide concretion (Fe2O3 / FeO(OH))

AI-generated identification · may be incorrect

Hardness: 5-5.5 (outer shell); Color: Dark brown to reddish-brown; Luster: Submetallic to earthy; Structure: Spheroidal/Concentric; Cleavage: None; Specific Gravity: 3.4-5.0

Hardness: 5-5
Color: Dark brown to reddish-brown
Luster: Submetallic to earthy

Identified July 6, 2026More sedimentary →

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Physical properties

Hardness: 5-5.5 (outer shell); Color: Dark brown to reddish-brown; Luster: Submetallic to earthy; Structure: Spheroidal/Concentric; Cleavage: None; Specific Gravity: 3.4-5.0

Formation & geological history

Formed through the precipitation of iron-bearing minerals (hematite or goethite) from groundwater within porous sandstone layers, often around a small nucleus like a sand grain or fossil. Typically associated with Jurassic period formations (like the Navajo Sandstone).

Uses & applications

Primarily used as metaphysical stones, educational specimens for geology, and occasionally used as a source of iron ore in historical contexts.

Geological facts

Commonly known as Moqui Marbles or Shaman Stones, these are found in large concentrations in the American Southwest and are famous for their perfectly spherical shapes which can range from marble-sized to cannonball-sized.

Field identification & locations

Identify by their round shape and heavy weight relative to size. Found in eroded sandstone plateaus. Collectors should look for a hard, dark crust covering a lighter sandy core.