While nickel exports are already one of Communist-run Cuba's main foreign currency earners, the cash-strapped country has untapped potential in other mineral deposits, according to the U.S. Geological Survey.

The $278 million Castellanos mine will produce annually 100,000 tonnes of zinc concentrate and 50,000 tonnes of lead concentrate, said executives at Emincar, the venture between Swiss-based commodities giant Trafigura and Cuban state firm Geominera.

"We are reviving the small and medium-size mining sector in Cuba from this investment," said Justo Hernández Pérez, Emincar deputy general manager, during a visit by foreign journalists on Thursday to the mine in the province of Pinar del Rio.

"This is just the start."

Many mines, including a gold mine at the site of the new Castellanos mine, were abandoned in the 1990s and 2000s in the wake of the fall of then key-ally the Soviet Union, the collapse of the economy and low commodities prices.

"We are now exploiting the deposit below oxide cap," said Emincar general manager Jose Vila, adding that it could prove profitable to once more mine for gold there.

The Castellanos mine holds reserves for 11 years of exploitation, while the nearby Santa Lucia deposit has enough for another 10 years, Vila said. Emincar will go on to exploit that deposit, tweaking its factory accordingly, once the Castellanos mine is exhausted.

In its annual investment portfolio released late last year, Cuba published dozens of opportunities for foreign investors to explore, exploit and commercialise precious metals, base metals and other minerals of interest.

Cuba hopes foreign investment will boost its economy that managed to climb out of a recession in the first half of 2017. The island is under severe strain due to lower exports and a drop in cheap oil shipments from ally Venezuela.

The Castellanos mine will employ nearly 500 workers. The average monthly wage at around $50, plus $80 in pay for good performance, is well above the average state wage of $30.

"This is a village that didn't have much work," said Guillermo Fabelo, a mechanic at the new mine whose father was a miner. "And this a project that will get many people back on their feet."

(Reporting by Sarah Marsh; editing by Diane Craft)

By Sarah Marsh