Sandstone for Utter Dummies

sandstone

We haven't figured out yet why some freelancers decide they're knowledgeable enough about a field to "specialize," but based on what we find at the various sites, some of them do. We know from insider secrets from eHow.com (now the many niches of Leaf Group) that some contributors liked to rewrite the same information multiple times, but why a freelancer would pretend to be an expert in earth science, but somehow Mary McMahon (formerly S. E. Smith) convinced the other English lit grads at wiseGEEK.com that she had the chops. As demonstrated, however, by "What Is Sandstone?" she did not.

We will start with words from the AN headquarters copy of the Dictionary of Geological Terms (ours is the second edition, © 1962):

"A cemented or otherwise compacted detrital sediment composed predominantly of quarts grains, the grades of the latter being those of sand."

The key words in that definition are "sand," "sediment," and "detrital," Our staff geologist opines that the mention of quartz is, in fact, misleading; the original author may have been attempting to differentiate quartzose sandstone from arkose and greywacke. But enough of that... McMahon says, and we quote, that sandstone is,

"...a type of sedimentary rock that forms from a compacted sand aggregate glued together with a mineral cement."

Clumsy, yes, but essentially correct except for failing to mention that "sand" refers to size and not composition. Unfortunately, Mary had to expand on that kernel of accuracy, presumably because WiseGEEK's SEO gurus required a minimum word count. As is often the case when the scientifically illiterate attempt to share scientific information, Mary's interpretation went awry. Here are a few examples:

• "...the appearance and texture of the rock can vary widely, depending on its composition and where it formed. " – A) she shouldn't use "texture" so loosely and B) "where it formed" is not as important as the environment in which it formed.
• "The formation of sandstone starts when a layer of sand or finely grained [sic] mineral particles forms, often by precipitating out of a river or stream. " – Ummm, no, sand does not precipitate from water. It  usually settles.
• "At the same time that the sand is being compressed, water trickling through the higher deposits carries minerals down, and these minerals start to glue the sand together. " – We strenuously disagree with the notion that cementation occurs top-down.
• "Young sandstone is very friable and crumbly, while mature rock can be extremely strong..." – Friability is not an indication of age, it is a function of the efficacy of cementation.
• "Because sandstone is so resistant to weathering, it often forms distinctive geologic monuments." – We have no idea what McMahon means by "geologic monuments." The term does not appear in our geologic dictionary...
• "It is also possible to find quartzose sandstone, which contains a very high concentration of quartz. " – Ummm, yeah. 'Nuff said.
• "All types are very porous, and the stone often protects formidable aquifers that can be tapped for water." –  No, not all types are porous, and we have no idea what a "formidable aquifer" is.

McMahon mentioned quartzose sandstone and arkose, and even babbled about argillaceous sandstone, but she never mentioned greywacke, apparently because she either didn't read that far in the Wikipedia article or because she was confused about the definitions of argillaceous sandstone and greywacke. Either way, our Dumbass of the Day was clearly out of her league trying to inform us about sedimentary rocks!

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