I'm planning to make a silver ring?

why is this question under relationships? it should be under craft and hobbies. you are obviously not trained in jewelery making or you would not need to ask this question. you should leave this type of high end jewelry making alone until you have done both a lapidary course and a gem setting course. there is a difference between sterling and non sterling in that sterling doesn't tarnish. you can't check without melting the silver, or damaging it in some other way. only a trained gemologist can tell the difference without destroying the gem. and most jewelers will not sell the materials needed to the general public, you would have to go to one of their suppliers, and they only sell to qualified jewelers. not only that but unless you already own the very expensive equipment, it is cheaper to commission a jeweler to make the piece