Informal A rich or plentiful source of something desired.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "gold mine" in a sentence
"'Before that I'm taking a look round a gold mine and then going to the Kruger National Park for a few days.'"
"Marci Burt and her potential gold mine of a landscaping client, sitting in one of the sunny front booths of Estia, sipped their lattes and let the deliciousness of the concept sink in."
"Columbus thought that he smelled Oriental spices, which Marco Polo had described as abounding in Cipango; when he walked by the shore and saw the shells of pearl oysters, he believed the island to be loaded with pearls and precious stones; when he saw a scrap of tinsel or bright metal adorning a native, he argued that there was a gold mine close at hand."