They range in size from fraction of an inch to several inches in diameter.
They are called moqui marbles.
The word moqui comes from the Hopi Tribe, and it means the dead in the Hopi language.
Moqui marbles in southern Utah.
Geologists call then concretion.
Flakes of iron-rich minerals blew in from the surrounding and became buried along with the quartz sand.
Eons later, the iron fused with the grain sands giving the Navajo Sandstone its amazing colors and patterns.
This iron-laden water eventually flowed to a place where the groundwater chemistry changed and caused the iron to precipitate.
Inside of a moqui marble.
Photo credit:MostlyDeserts/Wikimedia
Moqui Marbles.
In 2004, NASAs Mars Rover found concretion in Mars, which scientists have named Martian blueberries.
Photo credit: NASA/JPL-Caltech/Cornell Univ./ USGS/Modesto Junior College
Mars Rover tracks and Blueberries (false color image).
Photo credit: NASA/JPLCaltech/Cornell
Martian blueberries (false color image).
