Featured Silver amethyst marcasite ring

I think it is amethyst, as you originally thought.

 

I'm thinking so to- I just spent a couple mins holding it up in different lights next to an earring that I know is an amethyst and in a similar shade, and the seemed to look the same in the different lightings
I'd never heard of this glass that changes colour though- it's super interesting!

 

No colour change, so probably amethyst. I do like neodymium glass tho'.

 

Same here. I found some neodymium glass beads once by mistake - bought "purple" from a Chinese seller of modern glass and ...whoops! Can't say I was complaining.

 

Alexandrite will change under a pen light too. That would be a find.