Chalk for Dummies - The Freelance Files MMCLV

Modern coccolithophore

Today's nominee, making another of her frequent visits to these pages, is here in part because she demonstrated a failure to understand one of the most basic tenets of the earth sciences: a rock is not the same thing as a mineral. You can describe rocks in terms of the minerals present and their texture, but you cannot assign to them the physical properties associated with minerals. That the post Mary McMahon dumped on WiseGEEK.com back in 2008 (when she called herself S. E. Smith) contains multiple repetitions of  the same error, however, does not surprise us. Mary has long since proven that her grasp of earth sciences is quite tenuous, and "What is Chalk?" (now at AllThingsNature.org) is one more example of her scientific ignorance.

As befits her "liberal arts degree," McMahon rushed past the technical details of her post to get to a discussion of how chalk is used and what the stuff we (used to) write on blackboards with is made of these days. In fact, of the 350-plus words she wrote on the topic, only about eighty actually defined and described chalk (and we're being generous with our count). The remainder spoke of outlining tennis courts and marking fabric for alteration, among other topics. 

No matter the ratio of definition to padding, however, what irked our staffers most was that McMahon repeatedly referred to chalk as a "mineral" and even went so far as to tell her readers that, "The chemical formula for chalk is CaCO3." No, Mary, chalk is not a mineral. Calcite, which makes up the tests of the bazillions of microorganisms that died to give us chalk, is a mineral with the formula CaCO3; chalk is a rock. Rocks do not have chemical formulas. In fact, Mary referred to chalk as a mineral not once but at least five times. In addition, telling her readers that, "Its primary ingredient is ancient fossilized sea organisms..."

...isn't particularly surprising, given that one of the major building blocks of most limestones is "ancient fossilized sea organisms." Sheesh!

Mary blew it, however, when she decided to blather at length about the uses of chalk instead of actually describing it. Her readers do not learn, for instance, that the dominant "ancient fossilized sea organisms" in most chalk deposit are foraminifera and a tiny plant called a coccolithophore (see image above). Nor do her readers learn that the Latin word for chalk, creta, is the basis for the name of the Cretaceous Period; a moment in geologic time when chalk deposition occurred in locations around the world. This includes the White Cliffs of Dover, about which McMahon gushes at length; as well as chalk deposits in the northern Great Plains (Niobrara Chalk) and Texas central highlands (Austin Chalk).

Then again, Mary's readers wouldn't know that. Instead, they learned that,

"Tailors use chalk to make temporary marks on fabric and clothing."

Big whoop. They also use white soap. Then again, most tailors haven't qualified for Dumbass of the Day more than a dozen times... but Mary has.

SI - GEOLOGY