Calcite vs. Quartz for Dummies

Calcite rhombohedron on clear, prismatic quartz crystals

If we've said it once, we've said it a million times: don't exaggerate! Well, actually, what we've said something like 1097 times so far is, "Don't exaggerate your competence." By that we usually mean, "Don't use words you don't understand to describe things or processes with which you aren't familiar." Take, for example, freelancer and former teacher Yasmin Zinni and her Sciencing.com article, "Difference Between Quartz & Calcite": you'll find lots of... freelance fumbling... there.

Unlike many of our DotD nominees, Zinni didn't completely blow her eHow.com assignment. Oh, sure, she said some stupid and/or erroneous stuff, but much of what she wrote was technically correct, although apparently aimed at about a third-grade level. Take, for instance, her comparison of the chemistry of the two minerals:

"Calcite is made of calcium carbonate, a compound containing calcium, carbon and oxygen atoms. Quartz is silicon dioxide, a chemical compound with one atom of silicon and two atoms of oxygen."

So, why didn't Yasmin spell out CaCO₃ like she did SiO₂? Inquiring minds what to know! Well, not really... She also pointed out that

"Quartz is much harder than calcite. Quartz reaches 7 on the Mohs scale of mineral hardness, whereas calcite's hardness is 3..."

Which, except for that nonspecific "much," is technically correct, but shouldn't Zinni have mentioned that the two minerals are defined as 7 and 3 on the Mohs scale? Sure, she should have... There are other missteps as well:

• "Quartz is not associated with living creatures...": You forgot radiolarians and diatoms, Yasmin.
• "...quartz is more common as a component of igneous rocks, such as granite and basalt...": Quartz is actually fairly rare in basalt; in fact many basalts have no quartz at all.
• "...calcite and quartz are both found in hexagonal and pyramidal forms...": technically speaking, both are trigonal, not hexagonal; but the upshot is that the shape of a random crystal isn't diagnostic.
• Yasmin should have mentioned cleavage in calcite vs. conchoidal fracture in quartz... but didn't...

Overall, Zinni's post is typical of the writing of someone who  obviously just harvested random factoids from the internet. It emphasizes trivia, omits important material, and misuses terminology unfamiliar to a lay person. In other words, Yasmin exaggerated her competence, for which freelancing sin she is hereby named the Antisocial Network's latest Dumbass of the Day.

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