This page contains information regarding Star Trek: Discovery, and thus may contain spoilers.
While Captain Kirk and Spock were imprisoned on Ekos in 2268, Spock used rubindium crystals from the transponders implanted in their arms to improvise a crude, makeshift, and primitive laser cutting torch to escape. (TOS: "Patterns of Force")
Rubindium was necessary in the construction of the 23rd century Crossfield-class's transtator, making both internal and external communications possible. When the USS Discovery's transtator was damaged beyond repair in 3189, they were not carrying enough rubindium on board to reconstruct it, though a nearby settlement on The Colony had an ample supply of it. (DIS: "Far From Home")