Diamond bolts are Adamant bolts tipped with Diamond bolt tips. Diamond bolts can be created through the Fletching skill. A player must first have a Fletching level of 65 and take a cut Diamond and use a chisel with it to make 12 Diamond bolt tips. Attaching diamond bolt tips also requires a Fletching level of 65 and grants 7 Fletching experience per tip attached. Once the Diamond bolt tips have been attached, the Adamant bolts become Diamond bolts.
Diamond bolts can be enchanted through the spell Enchant Crossbow Bolt (Diamond) by a player with level 57 Magic. The spell enchants 10 Diamond bolts at a time, and once they are enchanted they become enchanted diamond bolts and gain the ability to pierce armour. This gives the bolts a chance of negating a sizable portion of their target's defence bonuses against Ranged attacks.