A map of space surrounding the Ikalian asteroid belt
The Ikalian asteroid belt is a ring of asteroids in the Kriosian system. Among the elements in the asteroids were actinides.
In 2367, Kriosian rebels, fighting to regain their independence from the Klingon Empire, hid in the Ikalian asteroid belt, using the actinides to hid from sensor scans. While hiding in the belt, they attacked a Ferengi and a Cardassian freighter. (TNG: "The Mind's Eye")