Neutronium

Category:Resources
This exotic metal with incredibly high tensile strength is used for high durability module fabrication.
Used in: Most tier-III weapons, engines, large bulkheads, etc.
(spoilers!)
 
Common sources: Bonuses from surveying Anomalies, salvage from Imperial technology derelicts (Talonians, etc.), purchases from Trade factions on the cheap (e.g. Aquarian Traders).
Remarks: The value needed to accumulate even small counts of Neutronium is not small. In the early game it's suggested to sell unneeded Neutronium for any needed Gold / Yttrium / Chiralite, etc. Savvy players may observe that there's nothing stopping a ship designer from researching Dreadnought Hull and then skipping straight from an Explorer bridge to a Dreadnought bridge, bypassing the need for that much Neutronium.
Trivia: Neutronium in science fiction is a contested subject. Neutron-degenerate matter (that which is theorized to exist at the core of neutron stars) is expected to be so dense that it would be impossible to collect or shape. Free neutrons are not stable, decaying on the order of minutes. Atomic nuclei containing two or more neutrons would be an interesting proposition: A metallic substance composed entirely of neutrons (no protons, nor electrons) might have mass, but would not be affected by electromagnetic fields. This kind of conjecture is interesting, but fanciful, as all observed examples of non-degenerate neutronium / neutrium / neutrite have decayed even more rapidly than the most unstable proton-lean or proton-rich elements.