Diamonds are some of the most sought-after items in Minecraft, due to their use in crafting the strongest tools, weapons, and armor available in the game. Diamonds are also some of the rarest items in Minecraft, found only in the deepest levels of rock. This makes diamonds extremely difficult to find and severely limits players' supplies of diamonds. This tutorial is intended to help players who want to obtain, maintain, and expand their diamond supply.
You must have an iron pickaxe (or stronger) in order to mine diamonds. A water bucket, an iron sword, iron armor, and other usual caving supplies are also suggested.
 Finding Diamonds
Diamonds can be obtained from diamond ore, an extremely rare block that occurs in 0.0846% of stone from levels 2-16. Typically diamond is found near dirt around layer 9. There are two methods for locating ore: by caving or by mining. Either way, you'll need an iron pickaxe to mine the diamonds (also any gold, emerald or redstone you come across). Although it may be tempting to use stone tools in order to attempt to save the durability of your iron tools, stone should only be used when iron is in very short supply. This is due to the fact that iron is relatively common and has a greater mining speed and durability than stone. Consider that because iron tools mine faster, it is possible to mine a certain amount of iron in addition to recovering lost iron in the same time it takes for stone to mine just the extra iron meaning that in the long run "conserving iron" actually wastes it. You'll also want a supply of torches and wood for more (you'll likely find plenty of coal along the way). If you're caving, you'll want the usual supplies for that, notably armor and weapons. Diamonds can sometimes be found in Village chests.
 By Caving
Caving is less resource-expensive (except in torches) than mining, but is more dangerous and time-consuming, since it requires you to explore a multitude of dark, monster-filled caves. To locate diamond ore by caving, simply explore any caves you find (either by locating surface entrances or digging) and work your way downward until you're below level 15 (the debug screen will help you check your depth). Ravines and shafts can provide shortcuts to the depths—creating a waterfall can help you get down (and back up) safely. Finding subterranean lava pools is a good hint that you're in the right depth range, but those are actually not the best place to find them—besides the hazard of lava, they can replace part of the ore body, leaving you with fewer diamonds to mine. (It's actually better to start mining whole stone, once you've established that you're at the right depth.) If you do see diamond ore veins exposed near a lava pool, use a water bucket to convert the surface of the pool into obsidian or cobblestone... then leave the area flooded while you mine. That way, if there's more lava under the diamond ore, the water will quench it before the lava can destroy your newly mined diamond(s). If you don't see diamonds immediately, don't give up - diamonds aren't considered rare for nothing. Search for more caves at similar levels, or switch to the next method: mining or searching for village chests.
 By Mining
Mining is safer and more reliable than caving, but consumes more tool-crafting resources. It also generates a lot of spare cobblestone, although in some cases this may be viewed as a downside rather than a benefit.
To create a diamond mine, first get down to the diamond layers. Besides following existing caves, you can just dig a vertical shaft, quarry, or staircase down to the diamond-containing layers (as you do this, remember the cardinal rule: don't dig the block you're standing on!). Most players prefer level 11, because that puts the "lava flood" at foot level. Deeper tunnels are likely to expose lava at head level or from above, but at level 11, lava will probably be exposed in the floor. This may block further progress, but probably won't flood down the tunnel! Once at your chosen level, begin branch-mining or mining long, level hallways two blocks high and one block wide. Sooner or later (often later) your mining will expose a diamond ore vein.
It's likely your mine will intersect several caves. Since any cave you locate while mining for diamonds is, by definition, at the right level for diamonds, it's a good idea to explore (and light) the cave before proceeding with your mine.
 By Branch Mining
First, get to layer 10, 11, or 12 as discussed in the previous section. Next, dig a 2-block-high, 4-block-wide, 4-block-long room. After that, make a 2-block-high, 2-block-wide, horizontal tunnel. Dig the tunnel at least 50 blocks long. Then, dig side tunnels with six blocks in between each. This means you get maximum efficiency (ores mined/blocks mined) while maintaining a good amount of thoroughness (ores found in a given area/ores in a given area). Collect all ores found. Place torches every 10 blocks. You will find diamonds with this method. Remember to put a double, or large, chest (made by placing 2 chests next to each other) in your 4x2x4 room; you will need to drop off some cobblestone when it hogs your inventory.
 Video Tutorial
This video shows you a popular method of finding diamonds, known "Branch Mining".
Video tutorial of alternate method known as the "PinWheel".
 Mining Diamonds
Once you find a block or vein of diamond ore, you'll need to mine it to get the diamond gem it contains. Before you do this, though, make sure the area is safe: after all, you don't want to lose any diamonds!
First, if you've located the diamond ore by caving, light up or block off any nearby dark areas so you won't get blown up or shot while attempting to mine. Next, dig away all blocks directly adjacent to the vein, both to expose the whole vein and to make sure the diamonds won't drop into lava and burn. A very effective method of preventing anything from dropping into lava is holding the Shift (crouch) key and W (forward) key, while mining your resource. This will both prevent you and your precious diamonds from falling into possible lava below. If you encounter any lava, get rid of it before you mine the blocks.
Now that it's safe to mine, use an iron or diamond pickaxe to break the blocks. The blocks will drop one gem each, unless your pickaxe is enchanted with the Fortune enchantment (Fortune III, the highest level, will make ore drop as many as four diamonds, and on average doubles the yield of a diamond vein). Remember to dig around diamond veins, as diamonds can form diagonally in the same vein.
Now that you have diamonds, it's best to proceed directly to a safe place to stash them in a chest; this could be your home base or a secure mining outpost. Be careful to make the chest secure from attacks by creepers, or your precious new-found wealth could go up in smoke.
 Using Your Diamonds
Now that you have diamonds, you can begin crafting some of the best items the game has to offer.
 Diamond Tools
Diamonds can be used to make Shovels, Pickaxes, Axes, and Hoes that work faster and last significantly longer than any other tools. Most players use their first three diamonds to make a diamond pickaxe, the only tool in the game that can harvest Obsidian blocks. Although a Diamond Hoe lasts longer than any other hoe, it grants no speed boost and is generally considered a waste of diamonds.
 Diamond Weapons and Armor
Diamond swords deal the most damage of any sword - eight points - and diamond armor protects the wearer better than any other form of armor. As with diamond tools, they also last longer than swords and armor made from lower-quality materials.
 Other Diamond Items
Diamonds are also used to make Jukeboxes, decorative diamond blocks, and, most importantly, Enchantment Tables, which allow players to convert Experience into valuable tool-improving enchantments. They can also be used as the ore to power a Beacon, but this is unnecessarily expensive and it is recommended to use emerald or iron blocks. If you are playing the Pocket Edition, you can use three diamonds with six iron ingots to craft a Nether Reactor Core.
 Maintaining and Expanding Your Supply
Once you've realized how useful your first diamonds are, you'll probably want more. To this end, you'll need to continue mining. If you want to become truly diamond-rich, though, you'll need to do a few other things first.
 Getting a Fortune III Pickaxe
You'll want to mine with the Fortune Enchantment on your pickaxe, preferably level III, for your next diamond vein, to significantly improve the amount of diamonds you get. Alas, this is not something you can rely on, but you can try. If you find a large diamond vein, you have an enchantment table, and are confident you can get a Fortune III, it might be worth waiting and acquiring the diamonds later.
Enchanting is somewhat complex, but here is how to bootstrap the equipment needed: You need to start with at least 5 diamonds: The first three will go for a diamond pickaxe. This lets you mine obsidian, and you need four blocks. That plus the other two diamonds will go for an Enchantment Table, but first you need to make a book. In fact, you'll need to make a lot of books, but you can start with one to get the table made.
For the books, you will need leather (from cows), and paper, from sugar cane. For the first book, you'll need just one piece of leather and three of paper (from three pieces of sugar cane). You can probably get those while setting up a cow farm and a sugar cane farm. If you don't already have a wheat farm, make one to breed the cows.
Once you've made your enchantment table, it will let you make small enchantments, but to get Fortune—let alone Fortune 3 -- you'll need to boost the table's power with bookshelves. You will need a lot of bookshelves, which will require a lot of books, in turn requiring a lot of leather and a lot of paper. (You'll also need wood for the bookshelves, so having a tree farm is handy.) See the Enchanting article for details of how to arrange those.
In order to get Fortune III on an iron or diamond pickaxe you'll need to use nearly 30 levels of experience points per attempt, so a Mob Farm will be handy. While advanced methods are possible, it's fairly easy to build the experience by simply camping at a suitably modified dungeon. It should be noted, that mining ores gives you experience too, and thus you may get a level 30 or so just by mining all the coal you find during chunk mining in one chunk. Enchanting books for Fortune III is a bad idea because, as of 1.5.1, there is only a 0.4% chance of getting Fortune III even at level 30. In contrast, a diamond pickaxe at level 30 has a 7.7% chance of getting Fortune III.
Even after all this building and grinding, it's by no means guaranteed you'll get what you want. If you get Silk Touch instead, you can also use that to collect diamond ore instead of gems. When you absolutely need a few diamonds (say, for a diamond sword), you can always place that many blocks and use another pickaxe to mine them... but save the rest of the ore for when you do get a Fortune pickaxe!
You can also use an anvil to combine weaker items of the same material, turning 2 Fortune I pickaxes into 1 Fortune II, and 2 of those into one Fortune III. Rename the working item early to cut down on retread penalties, and be careful about combining multiple enchantments—the cost can easily make your pickaxe unworkable.
Once you've got a fortune pickaxe, return to mining as usual, reserving this pickaxe for veins of diamond or emerald. (If so inclined, you can use it on redstone, lapis lazuli, or even coal, but using a fortune enchanted pickaxe to mine coal is considered a waste of durability.)
 Repairing Tools
Repairing two tools doesn't just add their durability up - it adds some extra uses as well (5% bonus, 12% for anvils). That can help extend your mining trips with non-enchanted tools. Remember that a crafting-grid repair wipes enchantments, so if you want to keep the enchantments, use an anvil.