Identifying 18K White Gold: What to Look For & Potential Scams

Question
I purchased a ring from a friend who use to work at a jewelry store with many locations.  I was told in the beginning it was 18k white gold.  The ring has no stamping saying what karat it is.  I brought this up to her and she got very defensive and said that it is real the store stamps it themselves and she didn't stamp it because it's a pain.  Then she told me it's 14k.  The question I have is do they actually stamp their own rings because I have researched and have found that there has to be testing and the manufactures stamp the rings.  I called a store at a different location and they said they don't stamp their rings.  She also said if I have a acid test done it will turn green and the greener it is the higher the karat.  Is this true?  Thank you so much for your time

Answer
Dear Shannon,
Acid will not harm gold, it is the norm for testing metal content.  It should not turn green!.  Sometimes rings do not have stamps and there are many reasons for that.  If the ring was sized the jeweler removed them. However there should be a karat stampings, it is the law, including the casters hallmark. It is very simple to stamp a ring. If you are really concerned take it to a Jewelry proffesional for an appraisal.
Sincerely
Jeanette Blacy G.G.