The crystal tool seed is an elven crystal that can be turned into the crystal axe, crystal harpoon, or crystal pickaxe, using 120 crystal shards and their dragon counterparts on a singing bowl.
The crystal tools start off at 10,000 charges and degrades like all crystal equipment. The maximum charges that can be stored is 20,000. One charge is depleted for each item that is obtained using the tool (duplicates from items such as the varrock armour do not deplete an extra charge). To recharge the tool, the player must load in crystal shards (this can be done before it is inactive as well). Dismantling a crystal tool will return the dragon equivalent and crystal tool seed to the player and doing so will lose all crystal shard charges that were previously loaded.
Players can also exchange the tool seed for 100 crystal shards by speaking to Amrod in Prifddinas' Hefin Inn.
A dangerous death in PvP causes the crystal tools to revert to their dragon equivalents which will then be dropped for the killer. All crystal shards will be lost as well.
Players who do not meet the Crafting and Smithing requirements for each tool can talk to Conwenna or Reese to sing the tools for them for an additional 60 crystal shards per tool.
For an exhaustive list of all known sources for this item, see here