As a previous posters stated, this recipe is slightly wrong. It should read:
Goldsmithing (52) Smithing (20) Yield: 1 Fire Crystal Iron Ingot x1 Mythril Ingot x2
Note that it uses TWO mythril ingots, not one. I did not test the one-ingot recipe, but the previous poster mentioned that it was a mythril dagger. I can definitely confirm that this 2-ingot recipe works though, as I just made two of them.
Incidentally, the smithing lvl is at least 18 (as I was getting skillups at 18), and is probably something in the vicinity of 20, given the use of the iron ingot.
I crafted several of these at level 48 goldsmithing and level 20 smithing (after making a mythril dagger first by mistake) and I got skill ups in both goldsmithing and smithing.