Sandstone for the Dummy Geology Student

The Antisocial Network's staff geologist looked at the title of today's DotD nominee and heaved a mighty sigh. His next move was to reach onto his bookshelf and pull out a copy of what is arguably one of the most important sedimentology books of the 20th Century, Pettijohn and Potter's Sand and Sandstone. He then laid his head on the tome and wept... as would any sedimentologist who'd been forced to read the eHow article "Characteristics of Sandstone," a bunch of nonsense cobbled together by John London.

London's been here before: in fact, he was one of our earliest DotD nominees for a ridiculous attempt to address the question, "What is Sandstone?" back in 2015. That's when he tried to tell people that sandstones are "cemented with... granite," and that arkose is more likely to be found in "basins caused by tectonic activity." Today, however, John's focus seems a little more narrow. No more accurate, to be sure, but more narrow.

First, though, let's tell people what the "Characteristics of Sandstone" really are:

Sandstone is a clastic sedimentary rock, that is, a rock composed of mineral and rock grains that have been eroded and transported. By definition, sandstone is predominantly composed of sand-sized grains of minerals or pre-existing rocks. The defining characteristics of sandstone are its mineralogy and texture; genesis is not part of the definition.
London's attempt to list the characteristics of sandstone resulted in some rather bizarre claims, including (but not limited to):

1. "Sandstone... is made of some of the most common minerals found on earth."
2. "Sandstone is composed of very small grains of minerals or rocks, usually the size of grains of sand."
3. "Sandstone is formed in two steps. First, sand layers accumulate into piles known as grus. Water or air sorts the grains of rock or minerals in these piles, and sedimentation occurs."
4. "The environment where sandstone components are deposited determines the nature of sandstone. The size of component grains of rock or minerals, how the grains are sorted and the structure of the sediment formed are some of the determinant environmental factors."
5. "Sandstones are divided into three large groups: arkosic sandstones that are composed mostly of granite; quartzose sandstones, or beach sand, that are made up of mostly quartz; and argillaceous sandstones that have a lot of clay or silt."

OK, That ought to hold us for now. Here are the staff geologist's comments and corrections:

Since the term "sandstone" denotes grain size, not mineralogy, this statement is nonsense. Besides, the most common mineral on earth is probably olivine, which is relatively rare in sandstone. We believe that "daffynition" is demonstrably circular (remember, "sand" is a size, not a mineral). Here, London assumed that a video he watched holds true for weathering + erosion + transportation + deposition for every sandstone. Utter bull... The "nature of sandstone"? Is this some attempt to mention sedimentary structures, bedding, stratigraphy, and other subjects which John is woefully unqualified to mention?

5. Arkose is not "composed... of granite," it contains a significant percentage of feldspar grains. As for "beach sandstone"? No, John, there is beach sand that is entirely calcite (Gulf Coast of Florida) or mostly lithic fragments (Hawaii). Oh, and the third type of sandstone isn't "argillaceous," it's lithic wacke or greywacke – it contains significant amounts of rock fragments.

Just another J-school grad who thinks himself capable of distilling "knowledge" and "facts" from whatever rubbish he reads on the internet... and just another Dumbass of the Day.

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