Yep, got the link. For anyone curious to the gem in question, click here!
There is a green variety of quartz called prasiolite. There’s debate whether or not prasiolite occurs naturally, but their have been claims of it being found in nature (like this specimen from Poland). Most that is on the market are done through types of different treatments.
Just like heating amethyst for citrine, they also can do the same with some amethyst (and other quartz) which instead can turn green. This is why a lot of people call it green amethyst, even though the name is not accepted by most.
There’s also the possibility of it being synthetic via the hydrothermal method. That process is one that probably needs its own post, but for now I’ll give two links you guys can read: one and two.
Because they say it’s amethyst in the description, it could be heat treated instead of synthetic. Some photos show the gem to be lighter, then one is pictured very dark. It’s hard to be 100% just by observing semi-quality photos, and is not the same as observing the gem in person. As well, I prefer minerals in their natural state than in a gem state, so that throws me off here and there.
Hope this was of help!