Calcite and Limestone for Dummies

calcite crystal

Part of our staffers' research rubric is backgrounding the writers we feature. That's mostly because we don't want to harp on minor grammatical mistakes by non-English speakers (although English majors are fair game...). We're especially peeved when we run across someone who claims to have the background for a piece of writing, yet botches the assignment. Such is the case of freelancer J. Lang Wood, who submitted "What Is the Difference Between Limestone & Calcite" to eHow.com. The post now lives (for some unknown reason) at Hunker.com...

In the real world, the answer is simple: calcite is a mineral (chemical formula CaCO₃); limestone is a sedimentary rock mainly composed of calcite. Given Wood's claimed "Associate of Arts degree in chemistry" – is there really such a thing as an associate of arts in a science? – one might assume she'd go straight to the science... and she did. Except that she got it wrong:

"Calcite is a mineral that occurs in the natural geological processes of the Earth. Calcite is a form of calcium carbonate, a type of calcium salt oxide with three atoms of oxygen bonded to one atom of calcium. Calcite binds with other compounds to create limestone which is used in construction."

See where J. Lang went wrong? We do: the chemical formula of calcite includes three elements: calcium, carbon, and oxygen. According to Wood, however, there are only two: calcium and oxygen.  But wait: calcite is "calcium carbonate" – where'd she put the carbon? She's recited (and botched) the formula for lime, CaO₂... oops.

Wood goes on to blather some elementary discussion of the physical properties of calcite, although she says nothing of its hardness, cleavage, or crystal structure; and fails to mention efferevescence. We assume that's because she didn't understand any of those properties...

J. Lang next applies her research chops to limestone, explaining to one and all that,

"Limestone is another form of calcium carbonate. It generally contains 50 percent of calcite along with other minerals such as quartz, clay, pyrite or other materials."

Wait, what? "[G]enerally contains 50 percent of calcite"? No, idiot, it always contains at least 50% calcite: any less and it's not even considered a carbonate rock. Oh, yeah, and it's not "another form of calcium carbonate" – it's a sedimentary rock! Oh, wait, she (kinda) figured that out:

"Fossils are often found in limestone-type rock formations."

Wood wastes much of her 400-plus word post telling people how limestone is used in construction, as well as at least one moronic claim about calcite:

"Calcite was once used for gun sites [sic] for armaments during the second World War." When she's done, however, her readers still don't know the difference between calcite and limestone, which is the primary reason J. Lang Wood is our Dumbass of the Day.

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