Sterling silver, Argentium, and even Fine Silver can all tarnish (albeit at different rates).  In order to preserve the polish on your piece and to delay the tarnishing process, there are a number f techniques you can use.  These techniques include carefully brushing a fine paste of baking soda and water over your peice then carefully rinsing and drying the piece on a regular basis, keeping it stored with a tarnish control tab that is included with your purchase, using commercial silver jewelry polish, etc.  Whichever technique you use, please be sure to check its potential impact on any cabochons, faceted stones, or other inclusions as some cleaners can damage these.