The Leatherworkers Guild is located in Gridania, and is Headed by Geva, who is pictured above.

How do you unlock Leatherworker?

You can become a Leatherworker by visiting the Leatherworkers' Guild in Gridania. If you have at least L10 in any combat class – you're on your way to fashion fandom! Updating your Cooking Gear is quite important if you're going to be crafting your own leve items.

Where can I get Alumen?

Alumen can be gathered by miners through mining. It is harvested from a level 20 node in Drybone in Eastern Thanalan.