“I am a person with two skin tones.”

That was what a miner told photographer Đồng Hiếu when he visited Quảng Ninh Province’s coal mines to document their life in photos.

Quảng Ninh has one of the largest coal reserves in Vietnam, but people have been mining here since colonial times, so the open-pit mines are all but spent. Now, to hunt for the “black gold,” miners have to descend deep into the earth.

Through Hiếu’s photos, we get a glimpse into the miners’ lives: the deep tunnels, the blackened faces, the incessant danger. Yet bright white smiles still flash on their faces, and tender moments of joy punctuate the days of hardships.

Morning in the mine.

Loading mine construction materials onto carts.

A tunnel leading to the work site several hundred meters below sea level.

A miner in a deep tunnel.

Meeting in the tunnel.

A cable system to transport miners deep into the tunnels.

After long periods spent inside the mine, workers are covered in coal dust. Occupational dermatitis is a major cause of disability in miners, in addition to lung diseases and asthma.

Miners put their cards here before entering the tunnel. It would be very serious if someone’s card is left behind long after the workday is over, as that would mean an accident may have occurred.

The "Happiness room": when families of workers from distant provinces come to visit, the company puts them in an internal lodging, affectionately nicknamed "Happiness room," for a maximum of three days.

Đồng Hiếu is a Hanoi-based photographer and lecturer at the University of Theater and Performing Arts of Hanoi. To view more of his work, visit his Facebook or Instagram account @donghieuphotography.