Gold is a chemical sample found in Cambridge Polymer Labs, initially found as unidentified sample 611. Once the sample has been loaded into one of the polymer coating applicator's sample to holder, the option 'scan loaded reagents' needs to be selected from its terminal in order to identify the sample by its chemical name. It is one of the two key samples required to produce piezonucleic power armor along with lithium hydride.
Other than being placed in the polymer coating applicator, gold cannot be removed from the player character's inventory.
Gold can only be found in Cambridge Polymer Labs. It is locked in the top floor room (C3), accessible from the hole in the ceiling in the room on the opposite side of the lab section or from the Expert locked terminal outside the door.