Element 115

The  is one of the four crystal Meteorite Artefacts found in Tomb Raider III. It was fashioned from a meteorite by Polynesians, that impacted upon Antarctica many years ago.

Taken from Antarctica by one of the sailors from the HMS Beagle to North America, it somehow was obtained by the U.S. Government, and it resided in Area 51 within an Alien spacecraft before Lara stole it.

Trivia

 * Element 115 is allegedly the power source for Alien space craft, reported by supposed whistle-blower Robert Lazar in the late 80s and 90s. Lazar claimed to have worked at Area51 Site-4 where he examined a Flying Saucer recovered by the United States Government. This served as inspiration for the Flying Saucer's main power source in the Area51 level of Tomb Raider.
 * Element 115 has also appeared in the game Call of Duty: World at War, and Black Ops 1 and 2's Zombies mode, as the very energy source that was used for weapon technology, teleportation experiments, and creating the zombies.
 * Additionally, an alien substance known as Elerium-115 plays an important role as primary resource in the X-COM franchise. It also appears to be crystalline in form and is highly sought after (and recovered samples are usually well-protected.)

Element_115