It can be used to duplicate Iron Ingots using a Tome of Alkahest.
Lapis Lazuli is used to craft blue items including Blue Stained Glass, Blue Wool, Blue Backpacks, Blue Fancy Lamps, and Blue Golden Lanterns. It is also used to create the dye colors Magenta, Purple, Light Blue, Cyan, and Cactus Green. The Lapis Brick block and Bluegrass block are also crafted using Lapis Lazuli.
Lapis Lazuli is also used to add Luck to a Tinkers' Construct tool.
Lapis Lazuli can be duplicated with the Tome of Alkahest.