When iron is exposed to atmosphere surface of the metal becomes brown but silver under similar conditions becomes black. Explain with equations?

PLACEHOLDER ANSWER - the answer is an explanation with equations. Iron rusts in moist air, forming brown hydrated ferric oxide, $$4\text{Fe} + 3\text{O}_2 + 2x\text{H}_2\text{O} \rightarrow 2\text{Fe}_2\text{O}_3 \cdot x\text{H}_2\text{O}$$. Silver does not react with oxygen this way, but reacts with traces of hydrogen sulphide in air to form black silver sulphide, $$4\text{Ag} + 2\text{H}_2\text{S} + \text{O}_2 \rightarrow 2\text{Ag}_2\text{S} + 2\text{H}_2\text{O}$$.