Farming "The Primordial" div card

So I was kinda shocked when I saw the prices of the Primordial Jewels this league and I'm not sure how I feel about spending my entire 10 ex budget on jewels just to get my golementalist build going.

That made me remember The Primordial div card and I'm wondering if anyone have any experience about farming it? Last league I turned it in randomly a couple of times from just playing the Atlas normaly which makes me assume the droprate isn't too rare.

Was wondering if anyone have any experience farming this card and wether the droprate is weighted differently on different maps.
Also, maybe this could be a viable currency farming strategy if the droprate of the card is consistent enough considering how outrageous the prices of the jewels are.

Wondering the same thing as you (Just started mapping and saw the prices of jewels)

Don't know about the rate drop but you can find it in the maps mentionned here only

https://pathofexile.gamepedia.com/The_Primordial