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Moqui Marbles, also called Moqui balls or "Moki marbles", are iron oxide concretions which can be found eroding in great abundance out of outcrops of the Navajo Sandstone within south-central and southeastern Utah. These concretions range in shape from spheres to discs, buttons, spiked balls, cylindrical forms, and other odd shapes.
The abundant concretions found in the Navajo Sandstone consist of sandstone cemented together by hematite (Fe 2 O 3), 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.
The ironstone concretions are recovered from exposures along streams, roadcuts and in active or abandoned coal mine areas. Most concretions are found among the shale and sandstone that was piled up in either a spoil tip of an older underground mine, or ridges of the later surface mining .
Ironstone (sandstone with iron oxides) from the Mississippian Breathitt Formation, Mile Marker 166, I-64, Kentucky. Ironstone is a sedimentary rock, either deposited directly as a ferruginous sediment or created by chemical replacement, that contains a substantial proportion of an iron ore compound from which iron (Fe) can be smelted commercially.
Iron formations can be divided into subdivisions known as: banded iron formations (BIFs) and granular iron formations (GIFs). [ 3 ] The above classification scheme is the most commonly used and accepted, though sometimes an older system is used which divides iron-rich sedimentary rocks into three categories: bog iron deposits , ironstones , and ...
Smelting of this limited iron source was only briefly attempted in conjunction with the lignite mining. The iron-cemented sandstone was found to be a durable and colorful building material on the treeless 19th century Plains. Historic 1860s buildings of Fort Harker (Kansas) and Fort Larned are constructed of this stone. The Dakota clays are ...
The geology of the region is dominated by the Weches greensand, which consists of glauconitic sand and clay. This greensand is underlain by various sedimentary formations, including the Queen City sand member and the Sparta sand. The iron ore is typically found in the form of limonite, concretions, or thin lenticular beds within the greensand.
At the Bisti/De-Na-Zin Wilderness, the Fruitland Formation consists mostly of gray shales, with thin coal beds and with resistant beds of white sandstones deposited in river channels. The formation also contains brown to purple iron concretions. In some places, the coal caught fire and burned to produce a red, hard rock, called clinker or red ...