Why does your silver necklace tarnish within a few hours?

Answer 1

Silver tarnishes because it reacts to the sulfur/hydrogen sulfur in the air. I assume that if the necklace is tarnishing so quickly it likely means that there is an unusual amount of sulfur or hydrogen sulfur in the air or, more likely, the reactant in the silver that causes ir to tarnish is found in an unusually high amount in that particular piece of jewellery.

Answer 2

Tarnishing is caused by the action of moisture, oxygen and acids in the air.

Hope this helps.