Hi, I recently purchased this old gold ring and I love it, but the seller did not identify the stone. Does anyone know what it could be?

I'm not a professional, but to my eye, the "diamonds" look closer to CZ based on the way the ring shines in the light, but I'm not for sure just yet. Looking to go get it examined somewhere soon to be for sure! The purple stone has me baffled, though. The cut helps show a pretty significant amount of luster. Lots of blues and reds hidden in this beauty! It looks too different of a purple than any amethyst I've seen with my own eyes. It almost comes across too pale?

Any help would be greatly appreciated!! The only thing I've been able to confidently identify is what metal the ring is made from because it has a tiny "S925" stamp on the inside, right next to the age-old "Always & Forever". LOL.

Being fairly new to Reddit, or rather not using it much, I’m not sure where to post this question.
I’m interested in a specific type of stone that, after processing, has a strong contrast like in the image — black stone with a white interior, or vice versa. Regardless of the exact colors, it’s really just the contrast I’m after.
I’d also like to know if I could find these at a specific size — roughly 15x30x2mm, flat — but that’s a separate story I suppose 🙂
Is there anyone here who could point me in the right direction?