File:Inside the Moqui Marbles (53234624816).jpg

English: My Moqui Marble just cracked open from a fall, and it looks like a Whopper inside. Named for the legends surrounding them by the Hopi (fka Moqui) Tribe, they mineralized underground from flowing iron-rich groundwater over a long period of time. They are found near outcrops of Jurassic-age Navajo Sandstone in Utah, where collection is now prohibited.

The dark ring of precipitated iron surrounds the softer white sandstone forming a spherical hard hematite concretion. Some recent studies propose that microorganisms later helped convert the precipitated iron into iron oxide.

The Opportunity rover on Mars found similar marbles. These Martian “blueberries” may have formed in a similar manner as the Moqui marbles on Earth, providing some of the first evidence for water in Mars’ ancient past (over 3B years ago) when Mars was wet enough to have river channels. And just like on Earth, these hematite concretions were found scattered on the ground and embedded in rock outcrops.

According to Hopi legend, our ancestors’ spirits return to Earth in the evenings to play marble games with these iron balls, and in the mornings the spirits leave the marbles behind to reassure us that they are happy and content. I like to think this extends to all of our worlds.

Sources:

• https://geology.utah.gov/map-pub/survey-notes/glad-you-asked/moqui-marbles
• Martian_spherules