The ore places are randomized in small extend (they appear in pre-set areas, but there are more areas that ore - so each game you may find them on other places... or not
)
And yep - you need to follow the main (crown) quest in order to get in the mines, so to get the griffon quest is not enough... still
I believe the Griffon King will give you this quest first when you return him his crown, what is possible only if you return from Freedom Islands, where you have to find the mine map... only if you returned from freedom islands w/o this main quest item - map, only then you can get "paint griffin quest" and not have the main quest done.