Lapis Lazuli

"A glimmer of blue in the dark wall of a cave - could it be DIAMOND? Ah, no. Instead you've stumbled on a seam of lapis lazuli ore. It can be fashioned into a fancy blue block (which can only otherwise to be found in the centre of Illager statues in Woodland Mansions), or into the dyes beloved of aesthetes who want to splash a bit of colour about. But it doesn't make for hardy armour, and for that reason, survival specialists may be disappointed to discover it."

- Alex Wiltshire

Lapis lazuli is a mineral used for enchanting or as a dye.

Mining
When mined with a stone pickaxe or better, a block of lapis lazuli ore will drop 4–8 pieces of lapis lazuli. With the Fortune III enchantment, a single block has a chance of dropping up to 32 pieces.

Trading
Cleric villagers sell 1–2 lapis lazuli for an emerald as part of their second tier of trades.

Enchanting
1–3 pieces of lapis lazuli are used to enchant items in an enchantment table.

ID
In bedrock edition lapis lazuli has the ID name, with a data value of 4.

Any number larger than 15 will result in bonemeal.

Trivia

 * In real life, lapis lazuli is a blue gem that may be ground and processed into ultramarine pigment. Lapis lazuli pigment has been famously used in the production of illuminated manuscripts, stained glass, and cave paintings. It was also used by Egyptians for their jewelry and other valuable items (see Wikipedia page).