Following the release of Fury of the Feywild on August 22, 2013 it became possible to "salvage" many epic level 60 items. This destroys the item and grants a quantity of in return.
The Salvage process is introduced to the player during the quest Salvage Operation, which leads to Hieronymous Glim, the Salvage Trader. Salvage can be performed in the area directly behind him and similar locations elsewhere in the game.
Open your inventory and right-click on an epic magic item - this will bring up the item options menu. If you are standing within the salvage area and an item is eligible for salvage, the "Salvage" option will be available.
Clicking on the Salvage option will bring up a window showing you the Rough Astral Diamonds you will get in exchange.