This metal is twice as heavy as lead but is unfortunately a property very few people will get the chance to experience. You see, iridium is breathtakingly rare and expensive. That it is mined at all is really only due to it riding shotgun as a minor "contaminant" of other precious metals, particularly platinum-bearing ores.

Most of the annual supply of iridium is turned into crucibles: shot glass-shaped molds that can withstand extremely high temperatures without melting or corroding. These crucibles are bank-breakingly expensive acquisitions for even well-funded laboratories... not exactly the type of item you expect to find on eBay.

Iridium is also notoriously difficult to work with. The metal refuses to melt (which again explains why they'd be made into crucibles) so shaping it requires special methods. While not brittle it is nevertheless very inelastic. An imaginary lengthy bar made of pure iridium could be made and when held up would shatter under its own weight rather than bend even a little.

While "only" as expensive as gold - currently a bit less, actually - the difficulties in manufacturing push it well past the price point of the yellow metal in finished products. These little cubes are no different and the king's ransom of a price for each reflects the high cost of labor and specialized equipment used in their making.

10mm cube weight is 21.9±0.3g. Larger cubes are possible on a made-to-order basis.