Diamond Ore

"There is one block in Minecraft that reliably quickens the breath whenever you see it (no offence, gravel, but it's definitely not you). One block that elicits a little "whoop!" of joy when you lay eyes on it, and the longest of "noooooooooooo"s when it falls into lava. Yes, you guessed it (probably by reading the title) – it's diamond ore!"

- Duncan Geere

Diamond ore is a rare ore that is the only reliable source of diamonds.

Mineral veins
Diamond ore can generate in the Overworld in the form of mineral veins. Diamond ore attempts to generate 1 time per chunk in veins of size 8, from altitudes 0 to 16, in all biomes.

Obtaining
The diamond ore block itself (rather than its diamond drops) can be obtained by mining it with an iron or diamond pickaxe with the Silk Touch enchantment.

Smelting ingredient
This recipe awards 1 experience.

Trivia

 * In some vein formations, ores connect diagonally.
 * In real life, the rarity of diamonds is highly exaggerated. Gemstone quality diamonds, whose qualities are mirrored by the game's mechanics, need to be cut and processed very carefully, and therefore need to be found in very large pieces. Industry-grade diamonds, which are used in the manufacturing of most diamond-based tools, are relatively plentiful and much more affordable.