Why is exploration for mining sites for extracting mineral resources like 'finding a needle in a haystack'?

Exploration for mining sites can be compared to finding a needle in a haystack because it involves searching vast areas of land for specific mineral deposits that are often invisible and buried underground. Just like searching for a needle in a haystack, it requires careful planning, advanced technology, and a bit of luck to locate economically viable mineral resources amidst a large expanse of earth.