WTN: cobalt
James Harbeck
cobalt
What colour is this eye?
I asked people on Bluesky, and I got various answers, including blue, blue-grey, and teal. Nobody said what I have always thought of it as: cobalt. Well, I suppose colour is in the eye of the beholder – literally, in this case, as it’s my eye.
Perhaps I’m being a bit fanciful in thinking it’s cobalt. I’ve always thought of cobalt as a sort of metallic, pastel-y blue, though apparently officially it’s not that metallic a colour… aside, that is, from being literally made from metal. The definitions are varying, mind you. For example, Wiktionary says it’s “deep blue” and shows a swatch of RBG #0047AB, which is also the colour given at the Wikipedia article, but it gives as a synonym zaffre, which is a colour the name of which is cognate with sapphire; zaffre is defined as the colour of the cobalt pigment, but it shows a swatch of RBG #00416A – somewhat darker, and perhaps closer to the colour of my eyes (which part, though?).
But if we’re talking about fanciful illusions, let’s talk about this name cobalt. It make seem like something cold, perhaps from the Baltic belt, or it may have computer echoes (as in COBOL, the programming language), but it’s a respelling of German Kobalt, which is taken from Kobold, which names a kind of goblin – from Middle High German kobe ‘shed, sty’ (nothing to do with beef) and holt ‘goblin’, which in turn is from hold ‘friendly’, which is a bit euphemistic; it means, more or less, ‘our little friend in the shed’.
And was our little friend in the shed blue? No. Our little friend in the shed was just difficult and noxious and disappointing. The goblin was in the details. You see, when cobalt ore was dug up and they tried to smelt it for silver or gold, all they got were a greyish powder plus arsenic fumes (as it happens, the primary cobalt ores always contain arsenic too). Insult and injury.
But usefulness can be in the eye of the beholder: while they didn’t get their silver or gold, the powder they did get could be sintered with aluminum oxide to make an good, stable blue pigment. (It can also be handled in other ways to make other pigments, such as cerulean.) So we think of cobalt as blue, though the metal itself is basically grey, and other molecules you can make with it can be black, brown, or even, as with cobalt chloride hexahydrate, red.
And yet, for a long time they didn’t know that cobalt was what was making the cobalt colour. What I mean is, they knew cobalt ore gave a powder that could be used to make the blue, but they thought the colour came from bismuth. It wasn’t until around 1735 that the Swedish chemist Georg Brandt saw the cobalt in the cobalt: he determined that it was actually a different metal, previously not identified – since cobalt never just sits there by itself; it’s always found in ores with other metals. It was the first metal to be newly identified since the start of recorded history. Quite something, the things that were there all along that you have to look twice to see.
And while cobalt is best known for its colour – a colour it doesn’t even have in its basic form – that’s not what it’s mostly used for now. It’s used more in alloys in such things as turbine blades, it’s used for producing radiation for therapy and sterilization, it’s used as a catalyst, it’s used in certain magnetic applications, and it’s used in batteries. In fact, the odds are nearly 100% that you have at least a few grams of cobalt within a very short distance from you as you read this, as the lithium-ion batteries that help power nearly all modern digital devices – among other things – use lithium cobalt oxide.
And although cobalt was first identified and used in Europe, the majority of the cobalt extraction in the world now is done in the Democratic Republic of the Congo, in mines that despoil the landscape and exploit the local populace, including children. Fortunately, cobalt is very recyclable; cobalt from old batteries can be extracted and used in new batteries, and increasingly that’s what’s being done. But it’s a reminder of the things we can’t see in the stuff of our daily lives – unless we look closely.
By the way, look closely at that picture of my eye. Do you see the reflection left of centre? Can you make it out? Look closely. Here’s a picture of what I was looking at.
What colour would you say those umbrellas are? How about the reflections on the table? To me, it’s elementary: I see the cobalt in the cobalt. But – as always – it’s in the eye of the beholder.
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