[noun] [C] - a place where gold or rock containing gold is dug from under the ground, or something which produces wealth or informationIf a restaurant were to open here, it would be a real goldmine (= would produce a lot of money).The archive is a goldmine (= contains a lot of interesting information) for historians.
GOLDMINE
Meaning of GOLDMINE in English
Cambridge English vocab. Кембриджский английский словарь. 2012