Mexican Black, or Black Gold (Not Oil - Coal).

Mexican business people moved into a new field, a coal field that is. The new wealth for an old product.

Mining is big business you can be a broker buy and sell without being in the business directly. A rich coal  area lays along the US border where you can produce or buy from small mine operators, then resell to a state-owned company at  a profit.

Along the way, besides the earth's black bounty, the new legal business people reaping credibility as now legitimate business people.

Mexican Mining Association says Mexico produces 15 million tonnes of coal a year, worth $3.8 billion. About 95 percent of it comes from Coahuila State.

The new investors reportedly produce or buy 10,000 tonnes of coal a week. Selling it at a profit, that might dou ble their investment.

Business diversification into the local economy  is a natural evolution.