This is likely the most exotic member on this page's lineup. Barium is an extraordinarily reactive metal that is so prone to oxidation that the property is actively exploited wherever oxygen (and other gases) are unwanted. This happens, for example, in devices which need to hold a vacuum. Rather than employ costly measures to avoid trapping all traces of contaminants it is often simpler - and equally effective - to place a small amount of barium in the vacuum where it will hungrily 'mop up' those undesirable elements.

While barium is a gray metal it is essentially a hopeless cause for the collector to retain a sizable amount of the metal in its unoxidized state precisely because of the difficulty of first eliminating every last trace of non-inert material from a container and then, if this much can be achieved, keep it sealed so well that nothing gets in. Realistically, it can only be done by sealing in sturdy glass with an ultra-purified noble gas like argon. Possible, but not within the means of most amateur hobbyists.

To guarantee that this very fragile metal does not degrade these cubes have been enclosed in glass ampules with argon gas.

10mm cube weight is approximately 3.5 grams.