Tarnish is a thin layer of silver sulfide that forms when silver meets sulfur in the air, in rubber bands or in some foods. It starts as a yellow tint, deepens to brown and then black, and it wipes away with a polishing cloth.

Oxidation in jewelry usually means a deliberate dark finish added to recessed details so that patterns stand out. It is meant to stay, so heavy polishing removes the design rather than restoring it.

Worn plating looks different again: a coppery or grey patch appears where a rhodium or gold layer has rubbed through, often on the underside of rings. Polishing will not help, and the piece needs replating.

This guide on tarnish vs oxidation shows photos of each and explains which cleaning method suits which problem.

If the piece is a ring that also feels tight or loose, it is worth checking the size at the same time. Here is a simple way of measuring your ring size at home with a strip of paper.