Subject just about says it all - if I need new smelting recipes, where do I go? Prospecting is confusing compared to Cook and Jeweler, both of which I "get". As a Tinkerer there is also no offering for a "Prospector's Guild" when I talk to the guy. Any comments or help appreciated.
There's no recipes for a prospector, you just advance in it by smelting your tier's resources. After going up a level you gain the ability to prospect and smelt new types of minerals.
There's no guild to prospecting, as there is no guild to farming or forester.
Professions in a vocation are divided into two types: "gathering" and "crafting". Cook, Jeweller, Metalsmith, Weaponsmith, Woodworker, Tailor, and Scholar are all crafting professions, while Forester, Prospector, and (in some respects) Farmer are gathering professions. With the exception of Farming, the gathering professions generally have no (or very few) recipes. Of course, there are some exceptions, such as decorations or bulk recipes from skirmish barterers. Still, in Prospecting and Forester particularly, there are really no utility recipes aside from the default ones you automatically get when you reach a new tier. There are also no forester or prospector vendors (which is why they use the Supplier). More notably, there are no guilds for gathering professions, whereas each crafting profession has its own guild (only one of which you can join at a time).
That is to say (long-windedly), as far as I know there is no type of mineral you need to buy a recipe from the supplier to smelt, and there is no guild for it either.
My advice to all Prospectors/Foresters, hit level 20, run some skirmishes, collect SMs, barter for bulk recipes, life is easy.
Seriously, bulk recipes save a ton of time. They have just as much a chance to crit as the normal recipes do, however you're A) not as likely since you won't be repeating the recipe as often, and B) when you do crit, it's much more beneficial. Sure, if you could crit every time with the normal smelting process, you'd end up with triple your amount, but what's the honest likelihood that you'd even crit on 5 out of 50 ingots?