In mining, a rich mine or vein of silver or gold; hence, anything which is a mine of wealth or yields a large income
You can refer to a sudden great increase in wealth, success, or luck as a bonanza. The expected sales bonanza hadn't materialised. = windfall. a lucky or successful situation where people can make a lot of money (from bonacia, changed from malacia , from , from malakos )
a sudden happening that brings good fortune (as a sudden opportunity to make money); "the demand for testing has created a boom for those unregulated laboratories where boxes of specimen jars are processed lik an assembly line"