Alien crystal

Alien Crystals are items which are added to Fallout 3 in the Mothership Zeta add-on.

They come in two variations; Small Alien Crystals and Large Alien Crystals. They are commonly found aboard Mothership Zeta and are the equivilant of Pre-War Money for aliens. It is possible, but unconfirmed, that this is the currency used by the Aliens.