Feldspar for Dummy Scriptwriters

Plagioclase crystals (no microscope needed)

If it weren't disappointing, even bordering on degusting, it would be hilarious to watch liberal arts majors flounder about while trying to explain science. Oh, sure, some freelance writers rise above their liberal-arts education through diligence – Mary Roach has a BA in psych, for instance – but the less time you give them to learn, the greater the likelihood of dumbassery. The eHow.com model of a flat rate for a 300-500 word post meant many of them hurried through their alleged research, and the result often looked like what Iain McLean scribbled down in the Sciencing.com post, "What Are the Products of the Chemical Weathering of Feldspar?" 

Our geology types say the answer is pretty simple: "Clay minerals." And to some extent, McLean appears to have figured that out. Unfortunately, he couldn't just give a two-word answer, so he had to pad it out to about 325 words. As has been so often the case with eHow posts, it's in the padding that Iain's ignorance shone through. Take, for instance, his opening paragraph, which begins,

"Feldspar is the principle ground mineral of granite, monzonite and syenite. It makes up approximately 60-percent of these igneous rocks and gives granite its porphyritic texture (a mix of large grains with intersticial [sic] smaller grains). "

Our comments?

• WTF is a "ground mineral"?
• Feldspar is the principle mineral of a lot more than just those three rock types.
• Granite does not have a porphyritic texture!
• The word is "interstitial," Iain.

Beyond that, McLean made a number of other errors in his attempt to transcribe whatever wikipedia article he was cribbing from, to wit:

• "Plagioclase is a sodium or calcium aluminosilicate, occuring [sic] widely in rocks as free crystals. " – No Iain, plagioclase is a sodium and calcium silicate, classified by the ratio of the two cations in its composition. And WTF are "free crystals," anyway?
• "Under a polarising microscope, plagioclase crystals are shown to be triclinic in nature." – We hate to point this out, but hand samples of plagioclase are also triclinic...
• "Orthoclase feldspar... occurs homogenised in rocks " – WTF does that mean?

• "Feldspar... begins to chemically weather when exposed... on the Earth's surface... The result in solution is Kaolinite [sic]." – We have no idea what "result in solution" is supposed to mean, but we do know that kaolinite is only one of the clay minerals resulting from the weathering of feldspars; others include smectites and illite.
• "The precise chemical nature of the kaolin will be defined by the nature of the original feldspar, that is, whether it was aluminum, sodium, calcium or potassium rich, as these are the ions that will have been dissolved in solution." – If the cations have been "dissolved in solution," then they're gone. So how do they control the composition of the kaolinite, a silicate whose only metallic cation is aluminum?

McLean's comprehension of the chemistry of feldspar weathering is... well, let's just say that there's no comprehension there. His level of incomprehension is more than sufficient to make Iain today's Dumbass of the Day in both the geology and chemistry categories. We'll give him a pass on the BritEng spellings (though they were supposed to be Americanized), although we really wonder why he didn't write about "aluminium"?

SI - MINERALS