Sha-Touched

Sha-Touched gems are items that fit exclusively in Sha-Touched sockets, much in the manner of cut gems. Currently the only items having Sha-Touched sockets are from Grand Empress Shek'zeer in Heart of Fear, and Tsulong, Lei Shi and Sha of Fear in Terrace of Endless Spring.

Sha-Touched gems are unique-equipped. Wrathion also provides a prismatic socket upgrade for any Sha-Touched weapons in Patch 5.1 via the Eye of the Black Prince.

Source
When a player completes the legendary quest Breath of the Black Prince (quest), they will be offered a choice of three Sha-Touched gems. After that they will be able to purchase additional gems (not necessarily for cheap).

List
There are three Sha-Touched gems:
 * Crystallized Dread
 * Crystallized Horror
 * Crystallized Terror

There are nine Sha-Touched weapons: