On a storefront in this diamond-rich section of eastern Angola, Angola Selling Corp., the country's sole official buyer of uncut diamonds, promises "spectacular prices" for stones.
But in the region's alluvial diamond fields, freelance miners, called garimpeiros, speak of exploitative and life-threatening working conditions. Garimpeiros at one site in this remote province recently paused for a day of mourning for two colleagues buried alive in the sandy earth while digging.
About 1,500 men clamber around a vast landscape of craters marking their claims. Saurimo, the provincial capital, is a three-hour drive away, so they sleep in the open or under makeshift tents.
Angola has more than 1,000 sites of what it calls "artisanal" diamond mining. Other countries with similar industries include Sierra Leone, Ivory Coast, the Central African Republic and Brazil. In Angola the garimpos, or digging sites, are usually named after the first garimpeiro to find a stone, or the first to die looking.
Angola's civil war ended two years ago, so it faces no restrictions on "blood diamonds" under the Kimberley Process, an agreement established with United Nations backing to staunch the supply from conflict zones.
But pressure groups are urging a crackdown on artisanal digging, which one group likens to bonded slavery.
"It's the last great dirty secret of the diamond industry, and not one they're rushing to address," said Alex Yearsley, lead campaigner with London-based Global Witness.
Civil wars in Angola and Sierra Leone, along with threats of a consumer boycott, helped prod the Kimberley Process into existence. Trade in diamonds financed the Unita guerrilla movement in the last and bloodiest phase of Angola's nearly three-decade war.
But even with the war over, some analysts say the industry still cruelly exploits workers.
"The Kimberley Process has no mechanism to keep a check on abuses that are carried out by, or with the complicity of, the state and its agents," South Africa's Institute for Security Studies concluded in a recent report on Angola's east. "Perhaps it is time to rethink the idea of what constitutes a 'blood diamond.' "
Garimpeiros typically work in groups of four, supported by a patron who provides tools or other support. With few employment alternatives in rural Angola, men flock to the garimpos.
Finding an uncut stone is a matter of luck. "It depends on God," said Jose Antonio, a 29-year-old who has dug for three months without success. If a garimpeiro finds a good-quality one-carat diamond, it might fetch $400, says a buyer for Ascorp. But the miner would pocket less than $100 after paying 25% to his sponsor and splitting the rest four ways among his digging group.
Local leaders say the industry has not benefited the region, which remains among Angola's poorest. Saurimo's primary school averages 70 children to a class. The town has an erratic power supply and a hospital bereft of medical equipment.
"The levels of misery here are the worst in Angola," said Eugenio Dal Corso, Saurimo's Roman Catholic bishop. "People are very much aware that the riches of this country are being taken out of the land."
Diamond-mining companies pay taxes to Angola's government, but little money makes its way back to the east. Although De Beers, the diamond group, suspended operations in Angola in 2001 after a dispute with the government, smaller foreign companies, including Petra Diamonds and South Africa's Trans Hex, work there.
The largest operator is Catoca, jointly owned by Angola's Endiama, Brazil's Odebrecht and Russia's Almazy Rossii-Sakha.
The companies employ security companies, some of which have been accused of brutally evicting garimpeiros. The industry has restricted locals' access to farmland, endangering the region's only other big industry.
In April, Angola's diamond industry faced international criticism when the army expelled thousands of immigrant workers, mostly garimpeiros, over the nearby border with the Democratic Republic of Congo.
Calls are growing for better regulation of the industry in Angola, where the government also faces pressure for more accountability in managing its oil industry.
"What we want is a transparent government that can manage resources for the benefit of the people," said Jose Pami, a local politician with the Partido Renovador Social, one of eastern Angola's biggest parties.
Global Witness runs a campaign targeting European diamond dealers on the issue of artisanal digging. So far, it has had little success. "We try to educate the diamond dealers as much as we can ... [but] they're just not interested," Yearsley said.