gold mine noun
plural ∼ mines [count] 1 : a place where gold is dug from the ground : a mine that produces gold 2 : something that has or produces a lot of something desired (such as money)
▪ When she was the manager, the restaurant was a (real/veritable) gold mine! [=it was very profitable] ▪ The library is a gold mine of information.
▪ When she was the manager, the restaurant was a (real/veritable) gold mine! [=it was very profitable] ▪ The library is a gold mine of information.
