Very very shiny rocks

I couldn't really tell you which is my favourite item in my little element collection, but these recent additions certainly catch the eye.

Chromium lumps

(They're not actually all that recent, but I forgot to write about them until now.)

These are lumps of chromium. Solid chromium.

UPDATE: As requested in the comments below, here are a couple of little (silent) video clips of the chromium lumps in the sun, plus a chunk of crystalline silicon carbide and a couple of enormous cubic zirconias:

As undisputed king of the element-collecting hobby Theo Gray points out, chromium is commonplace in the modern world, but only in ultra-thin electroplated layers on other substances. There's no need to use more than a super-thin layer of chrome to make some car-part shiny, because chromium in air protects itself from corrosion with a hyper-thin oxide layer, sort of like aluminium, but more so. The chrome oxide layer, unlike the aluminium layer, is so thin that you can't even see it, so chrome looks freshly-polished all the time.

Chromium lump close-up

This stuff is actually so shiny that it looks fake, like rocks spray-painted silver and given an outlandish name in an episode of Star Trek. It feels more real when you pick it up, though, because chromium is only a little less dense than iron. It's also nonmagnetic, and non-toxic.

Various chromium salts are bad news and can be made accidentally in the home, by for instance using a stainless-steel object as the sacrificial anode for electrolytic de-rusting. But the metal itself is benign.

This is more than can be said for what's next to the chrome on my display shelf, the block of Wood's metal I cast in a Lego mould. Wood's metal has both lead and the more dangerous cadmium in it.

(See also, mercury. Metallic mercury is not good for you, but there's no reason to call out the men in moon suits just because you broke a fluorescent light. Organic mercury compounds, however, are very dangerous. Methylmercury, which can get into your body via contaminated fish, is rather nasty, and dimethylmercury is absolutely pure unadulterated gold-medal-winning death on a stick.)

I got my chromium, and a few other trinkets over the years, from eBay seller "The Mists of Avalon" (on eBay Australia, on eBay UK). From their name, you'd expect them sell a lot of metaphysical wank - and yes, they do! But right next to their "Wiccan/new age/spiritual/pagan" and "Healing/metaphysical crystals" categories, though, they've got umpteen science collectibles, and the listings for those items don't even contain the traditional fanciful explanations of the supposed effects of the periodic-table sample you're considering buying on chakras and meridians.

At the moment, Mists of Avalon seem to be the only eBay dealer selling these nice rock-shaped chromium lumps. They've got one listing for chunks not unlike mine, and another listing for "more than 10" bags of smaller lumps. (They've also got a listing for some chromium powder, but you probably don't care about that.)

There are a few other eBay dealers selling chromium, and other element, samples of one kind or another (on eBay Australia, on eBay UK). There's SoCal Nevada, for instance; I've bought a few sciency knick-knacks from them, too. They currently have one tiny crystal of chromium, and a couple of big machined disks of the stuff.

Theo Gray's pals RGB Research will be pleased to sell you a hefty cylinder of high-purity chromium, of the same standardised 35 by 55mm size as the tungsten and magnesium ones I've got (they don't have any of the big tungsten cylinders for sale at the moment, though) for the trifling sum of $US325 plus delivery.

EBay seller iannhart (on eBay Australia, on eBay UK) has a selection of 35-by-55mm cylinders too (including some tungsten ones!), as well as other shapes and sizes of chromium.

I'd hold out for the rock-shaped lumps, though; they really show off the bizarre nature of this substance. Tungsten doesn't look like much; its special characteristic is its extraordinary density, making it a plausible stand-in for plutonium.

Chromium is more like frozen latinum.

6 Responses to “Very very shiny rocks”

  1. Major Malfunction Says:

    Just as the Sikhs are required to carry certain sacred ceremonial items on their person, so too I believe Geeks should carry as many examples of elements as possible.

  2. Joseph Says:

    Couldn't resist that tiny chromium crystal from SoCal, and a tiny titanium crystal cluster to go with it. Now I just have to avoid looking through all their listings, before I find myself knee-deep in element samples.

    They have a nice selection of minerals too...

  3. Slurpy Says:

    I've never tried it, but supposedly you can do a Goldschmidt reaction (thermite-like) with chromium oxide and aluminum.

  4. Popup Says:

    Are they real actual naturally occurring chromium nuggets? Or have they been moulded to that shape?

    According to the Wikipedia chromium can be found in metallic form, but it' appears to be pretty rare. And the pictures I've found look nowhere as nice as yours.

    Yours look more like artificially grown crystals!

    • dan Says:

      No, they're not "native" chromium, which as you say is very rare and not that great-looking.

      These lumps are either the byproducts of some process or other - electroplating, alloying or something - or an intermediate stage in some other process. "The Mists of Avalon" mention in their listings that some of these lumps have drill-holes in them, from when they've been assayed for purity.

      The list of things they could be used for, besides as ornaments, is probably pretty short. Most industrial chromium is never purified to metal; it's either shipped as a "ferrochrome" alloy with iron for inclusion in some other alloy such as stainless steel, or it's kept as a ghastly poisonous soluble chromate for use in electroplating.

  5. Paper Docket Says:

    Any chance we can see a video of the Chromium? The photo doesn't look all that awesome.

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