It's well-documented that copper sulfate can be introduced to certain fuels to burn green. If one was to scale up the fireworks, so to speak, then I'm not so sure how to explain the mechanics of it all.
While copper sulfate was the inspiration for this question, I'm by no means limiting answers to using it. Just aiming to explain green volcanic eruptions / lava by any scientific means necessary.
Question
Specifically, if a world is to have green-colored volcanic eruptions, then, geologically-speaking what kind of composition in the crust / mantle / atmosphere would be needed? Essentially, anything that is scientifically plausible is fair game.Bonus points: Would be nice to still have a habitable world for humans. Not strictly necessary however.