In Ground Zero, Thaelite is a red crystal that is found in the deepest recesses of the planet Stroggos. It appears to be a more potent and unstable variety of the blue crystal known as Steedium. Thaelite formations will explode if shot by the player.
The crystal is encountered for the first time in the mines, yet it appears later in the game as well. It appears that Thaelite is the raw material used for the creation of antimatter cores at the munitions plant, and is thus an important component for the construction of Antimatter Bombs.
Stepchild is known to have created an antimatter core from a large chuck of Thaelite ore.