1562 hits.
It takes exactly 1562 uses to use up a Diamond Pickaxe.
COAL, diamond, emerald, gold, iron, lapiz, redstone
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You will find, on average, 3 diamond ore per 16x16 'chunk' of terrain. The number of chunks in a world can be different depending on the game platform, and only a small number of chunks are generated at a time. On the PC Java edition, a map is 60,000,000x60,000,000 blocks, so 3,750,000x3,750,000 chunks. Multiplied by 3, there are roughly 42,187,500,000,000 diamonds in a Minecraft world. That doesn't include any diamonds which may generate in chests.
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To do this you have to down date your minecraft version, there are many downgraders out there and then change to name of the file you have the world named to world 1
There is really only one diamond with this name, the Koh-in-Noor Diamond.
From new, a diamond pickaxe will break after 1562 uses, making it 6.2 times as durable as an iron pickaxe. Note that breaking a block that a pickaxe is not optimal for breaking counts as two uses. Source: Minecraft Wiki
As of July 2016, 23,979,019 Minecraft PC/Java have been sold. That is an average of 13981 a day since Minecraft came out for PC.
There is only one significant diamond named the Hope Diamond.
You can either your invedit a mod or you could use an in game mod called too many items