Onyx for Dummies

Black onyx

The freelance contributors to the Demand Media group of content farms have long been derided for their weak grasp of basic facts, especially in science and technology. Apparently paying college liberal arts and journalism grads who aren't making enough as baristas to write STEM content doesn't quite work. Take, for instance, "retired" professional trainer Marie Mulrooney of Leaf.tv (a "retiress" whose profile picture looks about 23); back for her third award in "How to Clean a Black Onyx Ring."¹

We won't argue (much) with Mulrooney's instructions, since they're pretty much reworded directly from a website that sells jewelry. Of course, the instructions reinforce the idea that onyx is "porous," which is utter bull in a mineralogical sense. What the jewelers actually mean is that the polished surface of a cabochon or other cut might start looking cloudy if it gets too wet too often, but that's no problem in reality.

No, where Mulrooney drew the interest of our house mineralogist is with this bald-faced rubbish: "While black onyx does exist naturally, it’s very rare. As a result, most commercially available 'black onyx' is actually agate that has been stained black. " That's a rather strange statement, since according to our mineralogy guy onyx and agate are the same darned thing! They're both layered chalcedony (that's hydrated microcrystalline quartz). The difference is merely in the shape of the layers: agate bands are curved, onyx bands are straight. So any claim that onyx is "actually agate" is, scientifically speaking, redundant.

Now if Marie had mentioned that a lot of what's sold as onyx is actually calcite or sometimes obsidian, or had gone into detail about this "dye" process (no dye is involved), we might have been impressed by her research. But she didn't... and that's why she's getting another Dumbass of the Day award.

¹ The original has been deleted by Leaf Group, but can still be accessed using the Wayback machine at archive.org. Its URL was   leaf.tv/articles/how-to-clean-a-black-onyx-ring/

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