In Stargate SG-1:

The main element of which the Stargate is composed. This element is not found on Earth, but can be found on other planets such as Abydos. It's a very dense quartzite superconducting metal which is the only known element that absorbs Neutrinos. This absorption provides the energy to create the wormholes.

Being highly energetic, the element can be used to create reactors and to enhance weapons such as atom bombs. The presense of this element is usually used to indicate the presence of Goa'uld technology.