This right here is the absolute ultimate exotic addition to our cubes lineup. Thallium is the only downright scary element from the periodic table this side of radioactive materials you only hear about following nuclear catastrophes. It is estimated that as little as 1.3 grams of this metal ingested is enough to put you six feet under. If it were only lethal when swallowed that would be bad enough but thallium has the (extremely unfortunate for human life) ability to pass through unbroken skin. That makes simply holding it hazardous to one’s health and the main reason we don’t stock the metal in its raw form.

As if the chemical hazards were not enough to contend with, thallium poses a slew of technical challenges to bedevil an engineer contemplating fashioning gadgets out of it. It is both very soft and vulnerable to oxidation. Working with it means either consigning expensive equipment for sole thallium use or laborious processes to prepare and then afterwards decontaminate the tools used. All of this, and not least of which is the expense of the metal itself, contributed to this being one of the last elements that we’ve turned into a perfect cubic centimeter.

While we learned a lot during the manufacturing process in the end only a handful of these cubes were completed over the course of eight long months, a phonebook’s worth of emails and the coordination of two labs in different continents!

And to be honest, this finished achievement, well… let’s just say they’re not much to look at. Trapped in their glass ampules knocking about anyone who didn’t know better might mistake them for fifty cent fishing lead weights. But, truly, they are the fruit of a lot of work in the pursuit of the crazy goal of making a complete set of pure metal density cubes a reality. Short of this the only other theoretically possible elements yet to be made are of radioactive metals not available to the public and/or ones whose mere presence nearby would be an even worse idea healthwise.

It really should go without saying but of all our items this deserves the sternest precaution be taken for anyone considering buying one of these. This is not the sort of disclaimer to be taken lightly. Kept in this reasonably sturdy glass ampule you are safely shielded from one of nature’s deadliest concoctions by a mere millimeter’s worth of glass. It is a transcendental feeling to be this close to something so lethal made harmless by such a trivial divider. Its owner should treat it with exactly the same level of respect you’d have for, say, slicing through fugu fish or being handed a test tube full of ebola. We’re not kidding.

Note that the cube is immobilized at the base of the ampule to protect the edges and corners which if allowed to slide freely would get dented because of the softness of the metal.