With the help of a special NPC you can create slots in items for precious stones. 1-2 regular slots for PvP and PvE stones (result is randomly determined) and 1 extra, which requires the use of a special resource). Stones can be taken back out if you want. 4 of the same stones can be joined into one higher quality stone. As well as regular precious stones there are rune stones, which are only inserted into bracteates.