Rodinium was one of the hardest known materials and it was frequently used in the construction of spacecraft and fixed installations. In 2266, rodinium was considered the hardest material known to Federation science, more than 21.4 times harder than diamond.
The Earth Outpost Stations along the Romulan Neutral Zone had armor made from cast rodinium, although that proved insufficient to protect them against the attack of a Romulan Bird-of-Prey's plasma torpedo. (TOS: "Balance of Terror")
In real-life science, element 125 has yet to be discovered or synthesized. A placeholder name based on its number, "unbipentium", has been suggested to document the possible existence of this element. Some models of theoretical science have stated that heavy elements on this scale may be impossible to synthesize or reproduce, and cannot exist in nature.