sedimentary
Moqui Marble (Concretion)
Iron Oxide Concretion (Hematite-cemented Sandstone)
Hardness: 5-6 (outer shell), color: tan to dark chocolate brown, luster: dull/earthy, crystal structure: amorphous to microcrystalline, cleavage: none, specific gravity: 3-5
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5-6 (outer shell), color: tan to dark chocolate brown, luster: dull/earthy, crystal structure: amorphous to microcrystalline, cleavage: none, specific gravity: 3-5
Formation & geological history
Formed via chemical precipitation of iron-rich minerals (hematite or goethite) within pore spaces of sandstone, often around a small nucleus like a fossil or pebble. Most famous examples come from the Jurassic-aged Navajo Sandstone (approx. 180-190 million years old).
Uses & applications
Used primarily as decorative collector specimens, metaphysical 'shaman stones,' and in geological education to study groundwater flow in sedimentary basins.
Geological facts
Also known as Navajo Cherries or Shaman Stones; very similar spherical concretions were discovered on Mars by the Opportunity rover, where they are nicknamed 'Martian Blueberries.'
Field identification & locations
Identified by its spherical or disc-like shape, sandy interior, and hard metallic outer shell; commonly found in the American Southwest (Utah/Arizona) and various beach deposits where wave action erodes them from surrounding sandstone cliffs.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone (Quartz-rich)
Arenite (SiO2)
sedimentary
Sandstone (with man-made markings)
Arenite (composed primarily of Quartz, SiO2)
sedimentary