Xenosaga Episode III: Also Sprach Zarathustra

Go back to the floating landmass. as you make your way through the tunnels to break the giant stone that is in your way by knocking another one on top of it, you'll find two other stones to knock down. One of them shatters on the ground, the other falls on another purple stone below the one you're trying to clear from your path. If you broke it already, log out of the U.M.N. and go back in. at the first tunnel you come to, enter and go left, you'll find it in the shattered remains of the secondary stone you broke. You'll have to take it to the bunny on the elsa to have it refined to get shion's ultimate weapon.

-jason