Moqui Marbles (also known as Shaman Stones or Thunderballs) are sedimentary concretions. They form as sediments are laid down at the bottom of bodies of water. The moqui marbles have harder minerals than the normal sediment. The sediment layers then turn to sandstone. When the sandstone erodes away, the marbles are uncovered.

Some believe that moqui marbles have mystic or paranormal abilities. Others may simply prize them for their uniqueness and cool looks. Moqiu Marbles can be found where Navajo Sandstone formations exist. One of the best places is Southern Utah.