Platinum

Platinum was an element, number 78 on the periodic table. The planet Janus VI was rich in platinum, among other minerals. 

Very volatile over 30 &deg;C, liquefied platinum was used in NX class starships in combination with cobalt to line antimatter relays. There were about 2.5 milliliters in each relay. The crew of the once used a half liter of platinum stripped from the relays to pay the foreman of a trellium mining planet of for the privilege of seeing Kessick. 

While trapped in Earth's past, Spock required a "small" block of platinum ("five or six pounds...") to properly construct a duodynetic field core. A frustrated James Kirk assured him that this was something less than economically feasible. 

Platinum is not found on the planet Angel I, a fact that allowed the USS Enterprise (NCC-1701-D) find the survivors of the freighter Odin, who were hiding on the planet in 2364. Their leader, Ramsey, kept his wings for its sentimental values on a necklace. The wings were made of platinum.