Atlas Stones are a very valuable item. You can find them at Atlas Interfaces (formerly Atlas Stations). Talk to the large orb inside the station to get one Atlas Stone. You can get one Atlas Stone at every Atlas Interface you visit. They are worth 70k units after patch 1.03 (before the patch they were worth 270k). Other than selling them for money, they have no use in the game. A nice benefit of Atlas Interfaces is that they also give you two Warp Cells, teach you new alien words, and give you Exosuit blueprints.