If you're a seasoned minecraft player then there is no need for you to read this diamond tutorial.

As we all know diamonds are the most valuable gem in the game, but they are also very hard to find not unless your
theeeeeeeeeeeeeeeeeeee absolute best diamond finder in the GAME!
Diamonds tend to load within y15 and below, but sometimes diamonds can spawn above y15, but that's a very low probability of happening.

Okay after you've read that here's the easy way to find the diamonds.
First you're gonna want to find a deep cave or a ravine.
The drop down or mine down until y15 or below your best chance to find diamonds is in a ravine,near redstone, or near lava and obsidian.
As to reason why you need to do this is because you don't want to mine in a entire chunk area to find these.
As soon as you find 1 ore of diamond you need to dig around it to make sure there is no lava or a really long drop that could kill you.

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First rule of minecraft never dig straight down!

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If you are willing to mine around within a very large chunk you should use efficiency picks or TNT because those are the fastest yet most efficient way to do this.
I think there is a way to make a diamond generator-my "friend" told me, but I think he is lying!--would be cool though-.

There is also 1 option find a temple or jungle temple and find the hidden chests to get your rewards!