Would it even be allowed to ship natural resources from one country to the another? I do not think it would be allowed by the customs and you can even loose the minerals in customs. If ever this was allowed, that it might have been a most profitable business for a lot of people because you can easily purchase some minerals in a cheaper price in few nations and sell those in nations where the price for such minerals is high enough.

But, you surely have to get certified from the government before you could do so or it might even be considered as smuggling because transferring natural resources from one country to another without involving the country government is not treated something as legal. I am damn sure OP wants some legal source of income though.