When a copper vessel is exposed to moist air for long it acquires a dull green coating. Why?

When a copper vessel is exposed to moist air for long, it acquires a dull green coating. The reaction can be represented as 2Cu+underset("moist air")ubrace(W+X+Y) to Cu(OH)_(2)+Z W,X,Y and Z respectively

When a copper vessel is exposed to moist air for a long time, it acquires a dull green coating on its surface. The material of this green coating is a mixture of

When a copper vessel is exposed to moist air for a long time, it acquires a dull green coating on its surface. The material of this green coating is a mixture of:

A copper vessel kept in moist air slowly acquires a greenish coating over its surface. What is this due to ?