sandstone - naturally bleached white Navajo sandstone - teaching student specimens - UNIT OF 5 SPECIMENS
The Navajo sandstone ranges from pinkish orange to white, The color is due to an iron oxide coating on the sand grains. In some areas reducing fluids flowed through the formation, removing the iron oxide coating. In either case, because the Navajo was deposited during the Jurassic in an immense coastal and inland dune field, the sand grains are frosted - they essentially sand blasted each other. The frosted nature of the grains is characteristic of the Navajo and is easily visible under 20x magnification, though a student with sharp eyes can see this with 10x.
These sand grains were carried west from the Appalachians by a Mississippi-scale river system and deposited at the continental edge, in present day Utah. Deposited on beaches by the waves, the sand grains were picked up by the wind and deposited in a gigantic dune field similar to Egypt's Great Sand Sea.
The Navajo Sandstone makes up the cross-bedded cliffs at Zion National Park in Utah. Locally it is poorly to moderately well cemented with silica cement. These specimens are moderately cemented and will stand up to student examination, though grains of sand can be rubbed off. Near Hurricane, Utah, the Navajo sandstone is 2,400 feet thick.
The sand grains in these specimens are larger than those of a silt and will feel like fine sand to a student. It would be instructive to compare this sandstone with one is larger grained, with one that is cemented with calcium carbonate, and with different colored sandstones, as sandstone has great variety and a student should not see only one example.
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