In Minecraft, diamonds are able to be gotten from diamond ore which is a rare find found in about ~0.0846% of blocks in level 5-16. You are able to find them anywhere beneath layer 16, but it is most common to be found in layers 5-12. Usually, most players will find them through caving and mining. Talk about mining, what is the most efficient way to mine diamonds?
According to IGN site, a very effective way to be able to find Diamonds is to branch mine. This method will involve covering a lot of surface area by creating a 2×2 tunnel and digging individual branches out from it every third block. If you do this, you are covering a lot of ground quickly without breaking any unnecessary blocks.
According to Minecraft Gamepedia, branch mining is safer and more reliable than caving. However, it consumes more tool-crafting resources. Also, it generates a lot of spare gravel, cobblestone, dirt, andesite, diorite and granite. But, it depends on the player since it may be viewed as a benefit or downside.
If you are looking for another effective way to get diamonds, you are able to explore caves. This is also an effective and fun method to find diamonds. Caves sometimes are able to be massive absolutely and it is easy to find diamond ore with a lot of visibility. If then, you find a lot of lava in your way, you are able to use a water bucket to make easy paths.
Have you heard about the staircase method? This is a great way to get to the depths of the world safely and efficiently. You have to dig yourself down at a 45 degree angle which leaves a staircase pattern behind you with each step dig one block deeper than the last. You will return to the surface by merely jumping your way back up. The staircase covers many grounds and it is a widely used method to find diamonds and other minerals successfully.
If you are looking for the fastest ways to mine, you can choose blowing up TNT. However, it requires you to kill a large number of creepers for gunpowder and get a lot of sand. If you have a generous amount of TNT, you are able to either blow up one at a time, detonate a large clump, or put a block every five meters. TNT will drop 100% of its items as of version 1.14.
Talking about finding diamonds, for your information, diamond ore only comes up between layers 1-16. However, it is most overflow on layer 12. If you want to check what layer you are on, you are able to check the Y value on your map. It is F3 on PC and if you are on Mac, it is FN + F3. It will be able to be found in veins as big as 8 blocks of Ore. Frequently, lava comes up between layers 4-10. If you want to stay safe, you need to make sure that you have to stay above these players.