Dating for spiritualists
The stony spheres are concretions — sandstone balls cemented by a hard shell of iron oxide minerals.
Where the Navajo Sandstone loses its iconic peach, orange and red stripes, hundreds of round, iron-coated stones often litter the ground.Odd balls The moqui marbles' precise ages come from a radioactive clock.The iron oxide minerals contain traces of radioactive uranium and thorium, and these decay by expelling helium.Other rusty structures formed too, including discs, "flying saucers," pipes and flat plates.Spiritualists have endowed the marbles with "energy" and dubbed the distinctive shapes as male and female, making them among the only rocks with a gender.After the dunes were blanketed and buried by younger geologic layers, the iron enrobed the sand grains, giving the Navajo Sandstone its amazing colors and patterns.
[Image Gallery: Majestic Monument Valley] Eons later, the moqui marbles were born.
When a mixture of water and natural gas flowed through the Navajo Sandstone, it stripped away the rusty coating, bleaching the rocks from red to creamy white.
Chan thinks this iron-rich water crept through the sandstone until it reached a crack, hole or layer where the water chemistry was different and iron settled out of the water.
Sometimes, a treasure — like a bone or a shell — hides inside.
The moqui marbles crop up in the Navajo Sandstone in Arizona and in Utah's public lands, eroding from the spectacular white cliffs in Zion National Park and the Grand Staircase-Escalante National Monument. The iron stones appear almost black, with a pitted surface polished by blowing sand.
Quietly sitting and holding one in each hand is said to calm the spirit, just like meditation. "I do believe these are important resources, and the geologic landscape is our heritage." Cloaked in iron The Navajo Sandstone was once the biggest expanse of dunes on Earth.