How do you obtain Primordial Jewels?

[Zahnrad]

I'm planning on farming a set of them but the Wiki for them is not quite clear enough for me.

[The_Driver]

Well, they can drop like normal jewels (although the Anima Stone might be recipe only, but it's not considered primordial...), so they can drop almost everywhere. If you want a little more directed approach, look at the divination cards.

https://pathofexile.gamepedia.com/The_Primordial
Is a very close fit, there's more generic ones for jewels, but they tend to grant others. If you look at that items drop locations (see link above) you can see a few different maps. Try to increase item quantity and monster count on them, and try to use the preferred map system to gain more of those maps. You may opt to specialize in one of multiple of those maps, if you use the preferred map system, you may want to prefer them such as different tiers of maps all have preferred maps on them (so T14 would have preferred map A, T15 map B, T16 map C, so that even if you find "lower" tier maps, there's a good chance to drop with something that suits you)

Once you've completed a set, turn it in at Navali. Repeat until you're satisified with the result.

Note:
As always, if you'd rather trade for it, that is often the faster route.

[Arnold Mupt]

your farm project is too difficult, buy them in order of prerequisite, 3+1 then complete with some more as you develop your tree.

[Arnold Mupt]

Thanks TheDriver for the Div method.