Help with a name for a mechanic

[ilovesaprolings]

The mechanic is "Spend only mana produced by basic lands to cast this spell." (yeah it's Imperiosaur)
What does sound cooler to an english speaker? Untainted or Uncontaminated?

[void_nothing]

Those are both valid words. Untainted gets a bonus as a mechanic name because it's three syllables versus six. For keywords, you should have shorter and pithier names if you can.

[OneAndOnly]

Neither; nonbasic lands aren't contaminated. Adamant has already been taken, but something closer to that, I suppose.

[Mookie]

Of the two options, I would go with 'untainted' due to it being fewer syllables. That said, I will agree that it feels weird for nonbasic lands to be tainted / contaminated. I'd probably go with something more positive instead - maybe 'primal'? I could see 'pristine'. 'pure', or 'simple' working instead, depending on the flavor.

[Sporegorger_Dragon]

I second "primal", but I'd also like to suggest "basal", to tie it in with "basic".

[void_nothing]

Basal would be neat.

[Ryder]

From the already proposed words I like "pure" and "primal". Let me throw in "radical" and "native". Everything depends on the flavor.