Diamagnetic ore
From Memory Alpha, the free Star Trek reference
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 that Enterprise (NX-01) attempted to evade aKlingon D5 class battlecruiser included the fairly typical composition of methane ice, isolytic plasma and diamagnetic dust. (ENT: "Judgment")
