Argonite

Argonite was a precious mineral found only in deep space. Argonite mines were discovered on Ta and exploited by Dom Issigri and Milo Clancey. Space beacons were made entirely out of Argonite, and were therefore targets of the space pirate Maurice Caven. (TV: The Space Pirates)

Argonite was also mined by the Eurogen Butler Corporation on Dimetos between 2142 and 2151. (PROSE: Another Girl, Another Planet)

Behind the scenes
The DWU argonite is unrelated to the real world ™, which is a commercial fire suppressant.