How do you know it's pure silver? If that is the case it will have a 3 digit number inside of it, usually 925, which means it is 92.5% silver and 7.5% other metals (usually copper). This is the finest "sterling" silver. Pure silver isn't used because it is too soft, the other metals make it harder, therefore more durable. If it has no number than it is either white gold or stainless steel. "Spinners" as they're usually called, are usually made of sterling silver or stainless steel. Metal is important in magick. You can use any one of them in magick, but they have different properties.
I'm the worst person to sell jewelry to! You can't con or sell badly made jewelry to someone who can make it themselves. My friends and family drag me to shops to "check" what they want before purchasing it. =)
Once you confirm that it has 925 or tell me what is printed inside of it, I can give you a few ideas. If it has nothing inside, wet your hands and let it stay moist under the ring. Wear it all day, then see if your finger turns green. If it does turn your finger green, you have yourself a highly mixed alloy with few or no fine metals (possibly "silver plated"), this means it has a high copper content with maybe some alluminum, steel or nickel mixed in too to make it look silver...basically junk!