Protocite, found primarily on Proto Worlds, is one of the biggest 'da f*** is this?!?' things in the universe; this metal liquefies readily at even very low temperatures (>10K) and yet is seen as a solid all over; light and energy are gratuitously thrown off by it without any chemical/radiological processes; and it is (most importantly) not supposed to exist. By that I mean: it didn't come from our universe. Nobody knows who or what brought this metal here.
Because it generates so much energy, protocite is used in fuel and batteries. These can be (and are) used in ion and plasma weaponry to devastating effect.
When ingested, protocite is a Class XV (Immediately Life-Threatening) cytotoxin and carcinogen. It is highly radioactive and can kill in doses lower than that of polonium; thus, this material is best handled with especial care.
Protocite, due to its high value and toxicity, is rarely used for non-scientific/military purposes. The price of protocite is exorbitant thanks to its main location: highly volatile, mutagenic biomes.
Protocite (Geology tree).