Kelbonite

Kelbonite is a refractory metal which is capable of deflecting or interfering with scans and energy beams, such as transporters, and can be found naturally on many planets.

In the mirror universe, on New T'Karath, the walls of the Sakethan burial mounds located on the planet, contained traces of kelbonite mixed with limestone. In September 2371, this impeeded Jean-Luc Picard's ability to be able to transport himself away with a segment of the Stone of Gol. (TNG novel: Glass Empires: "The Worst of Both Worlds").

The mountains on Ba'ku colony world contained kelbonite ore, which in 2375, proved useful in preventing the Ba'ku from being forcibly relocated from their world by the Son'a. (TNG novelization: Star Trek: Insurrection).