KAI RYSSDAL: The Democratic Republic of Congo is one of the most mineral-rich countries in the world. But the geology that that gave Congo those resources also posed a couple of problems: specifically, some of Africa's most active volcanoes. One of them erupted all over the city of Goma in 2002. Lava pretty much destroyed the mineral-trading town, but it turns out all that red-hot liquid rock did have a silver-lining — an economic silver lining at that. Suzanne Marmion explains.

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SUZANNE MARMION: Mount Nyiragongo still looms above the town of Goma, its head lost in a smoky haze. At night the grey cloud glows an ominous shade of red. When it erupted four years ago, the volcano killed as many as 100 people and displaced half a million.

Local journalist Jack Kahorha was here when the lava engulfed the town. Driving through the once devastated town, he points out the place where the police station once stood. Impounded cars were locked behind a high fence.

JACK KAHORHA: "But all of the cars and the building were taken away by lava."

Still, Kahorha says, when the molten rock stopped coming, it wasn't all bad.

KAHORHA: "This volcanic area is very fertile. So you're going to find that beans, vegetables grow, and you can't imagine that this is lava."

Goma also proved to be fertile ground for foreign donors. Countries gave $40 million to help the displaced families. The money sparked a construction boom, and it's LAVA that they're using to rebuild: lava walls, lava houses, and even lava gravel to make lava roads.

Goma now has some of the best streets in the whole of Congo, a nation where less than two percent of the roads are paved.

KAHORHA: "These are made by women who are jobless, they spend the whole day collecting stones and pounding them."

In a lava field nearby, the black stones are as sharp as glass. Women chip away at the frozen black sea.

Pelazhay Nyabaday says that before the volcano erupted, she made her living herding goats. But when everybody had to flee, looters came and stole her animals. She says her life became difficult. She had to live off whatever she could get from begging. But then she heard about the lava business.

She can sell a bucket of the black rocks for a $1.50, more than a day's pay in Congo. It's hard work, but she takes pride in it. Jack Kahorha translates for Nyabaday as she points to a construction site nearby.

PELAZHAY NYABADAY [TRANSLATED]: "You can see the house which is over there are the result, everywhere you see, people are building!"

Today the economy is thriving as a hub for mineral trading. Luxury hotels have gone up and the population is booming.

In Goma, Congo, I'm Suzanne Marmion for Marketplace.