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Moqui Marbles

Mars blueberries
Photo by Shinichi Kato
See more of his outstanding mineral photos.

Moqui Marble is the term used to identify a marble-like concretion having a sandstone center encased in an iron oxide shell. These geological oddities litter the surface of the iron rich Navajo sandstone in southern Utah's Zion and Capitol national parks, Grand Staircase-Escalante National Monument, Snow Canyon State Park and the Moab area.

Moqui Marble
Core of a Moqui Marble.
Photo by Dave Crosby, geologist
Shaman Stone
Moquis remain after sandstone erodes.
Photo by Brenda Beitler, University of Utah
The marbles accumulate after the softer surrounding sandstone erodes away leaving the much harder concretion behind. They are mostly smooth, and are elliptical or round balls. They are also referred to as Moqui Balls, Hopi Marbles and Shaman Stones.

These iron oxide concretions exhibit a wide variety of shapes and sizes. Their shape ranges from spheres to discs; buttons; spiked balls; cylindrical hollow pipe-like forms; and other odd shapes. Although many of these concretions are fused together like soap bubbles, many more also occur as isolated concretions, which range in diameter from the size of pin point (.04") to a little smaller than a basketball (over 8").

Mars blueberries
Shapes of Moqui Marbles.
Photo by Brenda Beitler, University of Utah
Shaman Stone
Pipe-like iron concretions.
Photo by Dave Crosby, geologist
In the US, they are commonly called Moqui Marbles after the Moqui (Hopi) Indians who inhabited the lands where they are found. Found during the excavation of ancient ruins around the world, some archeologists believe they have been used for centuries by Shamans and other mystics.

According to one source, in the Hopi language, the word "moqui" means "dearly departed one." Legend says that the departed ancestors of the Hopi Indians of the Southwestern United States played games with these "marbles" in the evening when spirits are allowed to visit the earth. When the sun rises they must return to the heavens so they leave the marbles behind to let relatives know they are happy and well.

There are various theories about how Moqui Marbles were formed. Some geologists believe them to be ironstone concretions formed about 25 million years ago when significant volumes of groundwater flowed through permeable rock and chemical reactions triggered minerals to precipitate and start forming a layered, spherical ball.

A great deal of research has been conducted by Marjorie Chan, chair and professor of geology and geophysics at the University of Utah and her colleagues: geology graduate student Brenda Beitler and emeritus professor of geology Bill Parry, both at the University of Utah; geologist Jens Ormo of the National Institute of Aerospace Technology in Madrid, Spain; and planetary scientist Goro Komatsu of the International Research School of Planetary Sciences at G. d'Annunzio University in Pescara, Italy.

For those wanting more information about Moqui Marbles check out this paper published in the GSA Today, 2005, by Chan, et al. titled: Red rock and red planet diagenesis: Comparisons of Earth and Mars concretions.

In 2004, two Mars rovers (Spirit and Opportunity) landed on the Red Planet and began to send back surface images. Mars Rover Opportunity found this cluster of loose, BB-sized, hematite-rich spherules at its Eagle Crater landing site. NASA scientists coined the term "blueberries" to describe these oddities. Opportunity analyzed the composition of these concretions with its spectrometers. Hypotheses about their formation have contributed to the story of water on Mars.

Martian Blueberries
Concretions appear like blueberries in a muffin.
Credit: NASA/JPL-Caltech/Cornell University

In 2014, the popular theory about the formation of Martian Blueberries held that the blueberries formed as a result of the flow of water through rocks on the planet—the same way similar iron-rich spheres are formed on Earth. But researchers from the Hawaii Institute of Geophysics and Planetology now believe that the spheres formed from meteorites that broke up in the Red Planet's atmosphere.

Their findings published in the journal of Planetary Space and Science, Volume 92, stated: Mysterious hematite spherules, also known as "blueberries", observed at Meridiani Planum on Mars have been widely accepted as concretions which are formed by precipitation of aqueous fluids.

One of the biggest mysteries is that all observed Martian blueberries are limited in size with maximum diameter of 6.2 mm. In contrast, terrestrial concretions are not size limited. In this article, researchers discuss significant differences between Martian blueberries and Earth concretion analogs. Puzzling observations from Mars Exploration Rovers Opportunity and Spirit suggest that the spherules may not be concretions but are cosmic spherules formed by ablation of meteorites.

The perfect spherical shape of spherules, their observed size limit, and all other physical properties are easily explained by a meteorite ablation model. Evidence that some of these spherules are only a few years old strongly constrains concretion and other growth mechanisms related to aqueous processes that require the existence of water on Mars in its recent history. The large number of hematite spherules in Meridiani Planum may be due to a big rare iron meteorite impact event in this region sometime in the past.

"The meteorite theory explains all of their properties," lead researcher Dr. Anupam Misra said of the spherules, per National Geographic.

Rockman began selling Moqui Marbles in the mid-1990's. At that time very limited information was available about these unique concretions. One of our first contacts who provided information about the Moqui Marbles was Dave Crosby. We have listed some of his theories here as will as that of Dr. Kord Ernstson.

Dave Crosby, a geologist who did extensive research in the Escalante Utah area where Moqui Marbles are found originally hypothesized that a meteor impact scattered molten spheres which then condensed on sand grains. Upon closer examination he found no evidence of a meteor impact. He then developed a theory that involves rainwater dissolving iron and other minerals carrying them into the groundwater. As the minerals flowed through the groundwater, their ions were deposited around sand grains forming spheres.

To contact Dave about his theories on the origin of these unique geological oddities, e-mail him at or read Dave's latest article posted at

Dr. Kord Ernstson is a German geophysicist and geologist and since 2000 adjunct professor of University of Wčrzburg. He has specialized in metorite impacts. Many years ago he was contacted by Dave Crosby and they discussed how Moqui Marbles may have developed. In his opinion, the Leisegang phenomenon best explains their origin.


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