Grand Staircase Escalante National Monument - Moqui-Marbles
"The abundant concretions found in the Navajo Sandstone consist of sandstone cemented together by hematite (Fe2O3), and goethite (FeOOH). The iron forming these concretions came from the breakdown of iron-bearing silicate minerals by weathering to form iron oxide coatings on other grains." en.wikipedia.org/wiki/Navajo_Sandstone#Iron_oxide_concret...
We think you’ll love these