Board Thread:Lore/@comment-25954624-20150404151445/@comment-27723099-20150425162021

Dragons have some of the jewels from their hoard in their hide. So you could say dragon hide is as hard as diamond if the dragon has a great treasure hoard and spent long time resting on it. This is how dragons are seen in most classical dragon sagas, and Tolkien's world is based on these classical stories.