Decalithium

Decalithium was a highly rare isotope and element which was a necessary component in making Red matter.

The Romulan miner Nero large deposits of Decalithium on an unnamed barren planet and began extraction procedures as it held great value to the Romulan Star Empire. However, he ended mining operations after a supernova from the Hobus star erupted and began threatening the quadrant as well as Romulus itself.

In order to combat this threat, it was decided to make use of decalithium to create red matter in order to collapse the Hobus star into a singularity. However, the technology for processing the isotope was only present on Vulcan.