Moqui marble
MO-kee
Small, dark, spherical iron-oxide concretions found on the sandstone surfaces of the Colorado Plateau, particularly in southern Utah. They range from pea-sized to golf-ball-sized and litter the ground like scattered shot. Also called Moqui balls or Navajo berries.
Etymology
Named for the Moqui (Hopi) people of the region. The Hopi regard them as meaningful objects. Geologically, they formed when iron minerals precipitated within Navajo Sandstone and the softer surrounding rock eroded away, leaving the harder spheres behind.
Notes
Found also on Mars — the Opportunity rover photographed near-identical formations, which NASA nicknamed "blueberries."
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