sedimentary

Moqui Marble (Sandstone Concretion)

Hematite-cemented Sandstone (Fe2O3 + SiO2)

AI-generated identification · may be incorrect

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

Identified June 9, 2026More sedimentary →

Explore Moqui Marble (Sandstone Concretion) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

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.