Diamagnetic Ore
From Star Trek : Freedom's Wiki
Diamagnetic Ore is a diamagnetic mineral high in energy yield. Diamagnetic ore causes sensor readings similar to those of an atmospheric electrical storm or an industrial facility might produce. (ENT: "The Shipment")
In addition, these diamagnetic minerals, which can be found in igneous rocks, also produce diamagnetic fields that interfere with the normal operation of many technological devices such as communicators. (ENT: "Dawn")
The planetary rings of a planet in which Enterprise NX-01 attempted to evade a Klingon D5 class battle cruiser included the fairly typical composition of methane ice, isolytic plasma and diamagnetic dust. (ENT: "Judgment")