Is My Gold Ring Tarnishing? Causes and Solutions

Question
I recently gave a yellow gold engagement ring to my fiancee.  I'm American, but I live in Yangon, Myanmar and had the ring made in Yangon.  About two weeks after I bought it, she showed it to me and it appeared to be turning into some sort of regular gray metal color.  Over the next few days, the gray worked around the ring, beginning with the part that faces the inside of her hand until it covered most of the ring up to and around the diamond on top, but it's still a little yellow around that area.  To my very untrained eyes, it looks like the kind of pattern you'd see when gold paint or plating is wearing off of cheap metal.

However, she took it to a different jeweler here who scratched it, looked under a microscope, applied heat, and then told her it is indeed 18 karat gold, but that some soap or powder she's using is causing it to change color.  Further, this apparently happens to 1% of rings.  (They then offered to plate the ring for about 50 cents.)

I've read about cosmetics reacting with gold to turn the wearer's skin black, but this didn't happen in this case.  The yellow color simply faded and was gone.  Do you think their story has any credence or did we get cheated?

Thanks for your help.

Answer
Hey there Mike, Wow interesting to say the least. So the jeweler said it was gold, and only charged you 50 cents to plate it? Somethings quite fishy here in my opinion, which is the ring is a base metal product. 18k gold doesn't wear off to show any metal. The 18k gold is 75% pur gold and does not wear off under any circumstances except for maybe sulfuric acid. Is the diamond genuine? I would invest in a new mounting at a registered jeweler if I were you. Good luck with the ring and your fiance'.

Steve Kretser