Minecraft wiki entry for Diamonds, associated text: Now that it's safe to mine, use an iron, diamond, or netherite pickaxe to break the blocks. The blocks drop one gem each, unless mined with a pickaxe enchanted with the Fortune enchantment. Fortune III, the highest level, causes as many as four diamonds to drop, and on average doubles the yield of a diamond blob. Remember to dig around diamond blobs, as diamonds can form diagonally in the same blob.