In southern Utah there is found a true geological curiosity called moki or moqui marbles. They are named in reference to a native american tribe that used to populate the southwest United States, and who used them for games, ammunition for their slings, and shaman stones.
The stones are concretions of iron ore formed around a center of sandstone. They are trapped in the softer Navajo sandstone, and as the cliffs erode they are freed and gather in "puddles".
There seem to be many theories on how the concretions were formed. Minerals being deposited by groundwater, meteorites hitting the earth, or volcanic venting are the most popular. Some scientists believe they were formed millions of years ago during the Jurassic era when this area was under a sea. Similar stones, nicknamed "blueberries" have been found on Mars.
The following photo taken by Lane's dad shows hundreds of moki marbles being exposed as the sandstone weathers away
Click on the picture below to better see another curiosity Lane discovered on our hike