Neuranium

Neuranium was a metallic substance used to shield from radiation, and one of the heaviest and densest metals in the galaxy. A millimeter of it could stop most scanners, and it could even temporarily block lightsaber energy. However in order to cover a space as large as a cargo hold, it would be prohibitively heavy and thus inefficient to use. Neuranium was so dense that some gravity-sensitive species noted its warping of the space-time fabric of gravity itself that a large piece created.

It was used in thick walls of the Emperor Palpatine Surgical Reconstruction Center and as a lining on one of Palpatine's statues of the Four Sages of Dwartii.

For years, Palpatine's lightsaber was hidden deep within a cavity in the neuranium of the statue of Sistros. The neuranium core of the statue was even able to resist a lightsaber blade activated inside it for several seconds. In these seconds, the neuranium glowed magenta to blood red to crimson before Palpatine's Sith saber lanced out of its core. Palpatine then extracted the lightsaber with the Force and hid it within the sleeve of his cloak for the inevitable battle.

Text and facts from the “Neuranium/Legends” article on Wookieepedia, licensed under CC BY-SA 3.0. Modified for this site.