Coltan is used to make pinhead capacitors - an essential component in mobile phones

It is then washed, crushed manually in a big pestle and mortar and tested again for iron ore before being fed into a photospectrometer to test its tantalum content.

The men concentrate calmly on their work or joke among themselves.

Blood tantalum

It is a far cry from the drama of the "No blood on my cell phone" campaign that a group of NGOs and religious communities have launched in Europe to lobby for an embargo on so called "blood tantalum", the colombo-tantalite ore that comes from the war zones in the east of the Democratic Republic of Congo.

Tantalum is essential in the manufacture of electrical components known as pinhead capacitors.

These regulate voltage and store energy in mobile phones, tens of millions of which have been sold in the past few years.

The European lobby groups, like the regional analysts, say that coltan production is fuelling the war in Congo.

Coltan

Jan. 2000: Coltan fetches $40/lb Dec. 2000: Coltan fetches $380/lb July 2001: Coltan fetches $100/lb 80% of production in Australia 80% of reserves in DRC

Such allegations infuriate both the rebels who control this part of Congo and their Rwandan backers.

They baffle the men on the ground in the coltan business, too preoccupied with making a living.

"It's our only way of making a living," said Blanchard, an intermediary who travels upcountry to buy coltan from the small-scale miners and brings it back to Goma to sell. "There's nothing else to do here."

Most of the men now in the coltan trade used to be farmers.

Bandits

Local human rights' groups say that coltan production does lead to security problems.

They say it is not uncommon for a miner who has just sold, say, $200 worth of coltan to be visited by bandits in military uniform who know exactly how much money he has in his house.

Foreign criticism of child labour in the coltan mines must be put into the context of Congo.

Coltan miners are worried by the recent fluctuation in its price

It is a country where the preoccupation of the average peasant is finding enough cassava to eat for the day.

If children were not helping mine coltan they would be working in the fields.

What would be cause for concern in the long term is if coltan were to be such big business for so long that the peasants forgot their farming skills in the way that some Central African villagers have forsaken logging for oil jobs.

When the coltan or the oil reserves run out they no longer have any means of livelihood.

Given the recent slump in coltan prices on the world market that scenario no longer seems so likely.

Local people say the price drop has had a disastrous effect on the region's economy.

"It's been a catastrophe," said Antoine, a local businessman. "I would estimate that 80% of all business here is either in coltan or dependent on the coltan trade and there's just a lot less money in circulation now."