The tell tale sign of a synthetic is it being essential “flawless” under x20 magnification. Natural gemstones are rarely without inclusions.
The other sign from the flame fusion process is what’s called “curved striae”. Can be a bit tricky to detect but you need a loupe for magnification and a bright light.
Because the growth process of flame fusion synthetics is like “drip drip drip” it creates “lines” in the material. Natural gems don’t have these type of lines. You might also see fine air bubbles as well but that often requires higher magnification.
Thank you so much!
Are you going to show us a picture ?
I finally found it! Set in a non precious metal in vintage style, I‘m almost 100% certain that it is synthetic. I was thinking to set it in a rose gold bezel, but it might not be worth it. It looks nice with a deep red colour, but I don’t wear it because the pendant keeps turning. But if I reset it, it might bother me to know it‘s synthetic...