This datapack adds simple crafting recipes to turn diamond tools and armor back into raw diamonds. You can salvage your diamond items by putting them in the crafting table to receive majority of the diamonds you used to make the tool.
Helmet -> 3 diamonds
Chestplate -> 5 diamonds
Leggings -> 4 diamonds
Boots -> 2 diamonds
Sword -> 1 diamond
Pickaxe -> 2 diamonds
Axe -> 2 diamonds
Shovel -> 2 sticks (to prevent infinite recycling of shovels)
Hoe -> 1 diamond