Rockhounds should look for anything special, not necessarily what they first start out searching for. An intense gold interest may blind a person to something common yet wonderful, right under their feet. Sedimentary rocks and their related formations are a good example.
Erik Christiansen and Kenneth Hamblin say that a rock formation is, “A distinctive body of rock that serves as a convenient unit for study and mapping.” The USGS goes a bit further, writing that, “A rock formation is a body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it.” Sedimentary rocks are usually named for the formation they were found in. There are hundreds of sedimentary based formations.
To serve as an example of a sedimentary rock and its related formation for my book, I bought the treated sandstone you see pictured below. It’s about three inches by five. It shows what can be done with a common rock, transforming it into something that rivals fine wood grain in its beauty. Being sandstone, it was assuredly easy to slab it with a rock saw into a square.
The seller’s description reads as follows:
“This is natural sandstone that formed 180 to 220 million years ago by wind and water as part of the geological formation ‘Shinarump.’ The colors and design were induced by a mineral spring containing iron oxides. If you like the unusual and beautiful works of nature, you will enjoy this picture sandstone product. Truly ‘Nature’s most beautiful painting.’ This piece comes from northern Arizona. The design and patterns are natural, its color is achieved by heat treating the stone. This caused the iron oxides found naturally in the stone to react, the richer the iron the deeper the color.”
Wikipedia has this good introduction to the Shinarump conglomerate, which is found throughout the Colorado plateau. You can read it by clicking here.
