How to Transmute Your Useless Materias to Other Useful Materias in FFXIV: ARR

We all know that farming materia is boring and will take a long time to get the spiritbond to 100%. After a long time farming, if you convert it to a wind materia or fire materia, do you feel disappoint? And how do you deal with those useless materias? Sell them to vendors, or just let them lay in your bank? Now the game lets us to transmute junk materias to other materias to make FFXIV Gil or save your FFXIV GIL. 

First, find the materia NPC, teleport to Black Brush Station. Then go to the Bonfire which can be found in the north of the Black Brush Station.