Natural ruby? FROM GOODWILL?!?!

I was at goodwill cruising around the other day and bought this ring for $2.00 for my fiancé. I took it home and just for giggles tested the ring with my presidium and it registered ruby; so the next step is of course to put it under a microscope and see if it has inclusions and it DOES. I have since tested the gold as it does not have any hallmarks on the inside and its 10k white gold. The ring also has six small diamonds on both sides. Biggest questions for you guys is do you also think it is natural? What’s it possibly worth?