By Mark Doyle
World Affairs Correspondent, BBC News
A diamond industry watchdog has called for stricter controls on gemstone exports from the Democratic Republic of Congo (DRC).
Diamond revenue is drained away from government, the report says
About $700m - estimated to be half of Congo's foreign exchange earnings - comes from the diamond trade annually.
But a study by Partnership Africa Canada said more could be generated if the mining sector was not dominated by exploitative practices and corruption.
Recent democratic elections gave an opportunity for transparency, it said.
While the official value of the sector is comparatively small - less than the turnover of a medium-sized international company - it is below the true value of the gems, the report says.
The Canadian and Congolese researchers suggest that much more could be generated by the industry - bringing in desperately needed revenue for schools and hospitals.
The report said that the industry revolves around diggers - those who usually are poorly paid to cut holes in riverbeds seeking the precious stones.
However, there is a web of people who make money from the sector, the report says, with government officials, traditional chiefs, soldiers, rebels and foreign buyers all living off the backs of the diggers by extorting a percentage.
The report calls for stricter application of existing laws to stop smuggling of diamonds.
Other recommendations include training more Congolese diamond valuers, to discourage middlemen from illegally undervaluing stones, and suggests ways of co-ordinating the fight against fraud.
The study says that the measures could work because last year's UN-backed elections meant there was now greater public input into government policy in the country Congo than at almost any time in the country's history.
But the authors are also realistic, citing a smuggler who described how he slipped diamonds out to Dubai.
And they quote a Congolese mathematics graduate, working as a digger, who described conditions in the mines as "worse than in the Middle Ages".