Why does silver tarnish, and how can you tell real 925?

Real sterling silver tarnishes because of sulfur in the air, which forms a thin dark film on the surface. That film is normal and completely reversible, and it says nothing about quality. Stainless steel and silver-tone costume pieces resist tarnish, but they are different metals with a different look and feel. The table below is measured from our own catalog, comparing what we carry in each.

Skin occasionally turning slightly green comes from the small amount of copper that makes sterling durable, reacting with sweat. It is harmless and washes off. On gold-over-silver pieces, called vermeil, unusual green or orange marks usually mean the gold layer has worn at contact points and the silver beneath is showing through and tarnishing there.

To check whether a piece is real sterling: look for the 925 stamp, and try a magnet. Silver is not magnetic, so a chain that snaps to a magnet is not sterling. For a piece with no stamp, a jeweler can test it in minutes.