There is another area. There is a dungeon on a beach near starting area. Inside this dungeon is at least 2-4 sulfer nodes, coal nodes, and metal nodes. Level 13 dungeon that isn't listed on your map. Directly south of Plateau of Beginnings, easiest path through the ruins, Dungeon is on the beach.

@Persuasion
If you're colorblind, I'd suggest whipping out your active pal and aiming at the node in question. It will first let you know whether or not your pal is able to complete a task if you throw (assign) it to that area. Second, it will identify the material the node is made up of. Apparently ore is Copper according to this method. So if it distinguishes between rock and copper, it'll tell you if it's sulfur in plain text.

I'm colorblind how do I know its Sulfur