Superman The Movie! Rare green prop crystal was used in the production of the 1978 film Superman The Movie. It is made of resin and was used primarily for stunt purposes, specifically when young Clark Kent (played by Jeff East) would throw the crystal into the icy Arctic tundra to create Superman’s Fortress Of Solitude. The crystal was also seen in Superman II, when Superman shows it to Lois Lane. The letters “FS” (Fortress Of Solitude) are etched into the bottom of the crystal. Comes with a signed letter of authenticity from Ilya Salkind, the producer of the Superman films.