Their eyes shining from dust-white faces latticed by trails of sweat from working hundreds of feet underground, the thousands of miners who burrow into a rebel-held hillside know the risks – and are prepared to take them to earn a few dollars a day.

Dragging sackfuls of columbite-tantalite, also known as coltan, to the surface via makeshift shafts at the Rubaya mine, in the eastern part of the Democratic Republic of the Congo (DRC), is dangerous.

So much so that, in late January this year, more than 400 of the young men who toil there were buried alive when the side of the mine collapsed down the slope. Hundreds more are feared dead following a second collapse at the beginning of March.

Run by a rebel group known as M23, which is backed by neighbouring Rwanda, with thousands of troops armed with weapons including anti-aircraft missiles, the mine lies in a region that has been at the centre of successive civil wars and invasions since 1994.

In the 30 years since, more than $50bn (£37bn) of aid has been funnelled to the country, but it has done little to solve one of the world’s most prolonged crises, recently compared by Donald Trump to the Second World War.

Now Rubaya, along with the vast mineral wealth of the rest of DRC, is at the centre of Trump’s efforts to secure long-term supplies of critical minerals to support the US economy.

Over the past year, Trump has threatened to take over Greenland (which is Danish territory), toppled Venezuela’s president, and exploited Russia’s war with Ukraine in an effort to secure access to the raw materials that US modern industries demand. His war on Iran may set these efforts back, but his strategic intent remains – he wants to make foreign mines his.

The east of DRC is rich in tin, gold, timber and other resources that have attracted opportunists and multinational corporations in equal measure since the collapse of the dictatorship of Mobutu Sese Seko, in what was then Zaire, during the mid-1990s.

Above all, the region has been a lucrative source of foreign currency for Uganda and Rwanda, a few hours’ drive away across the nearby border.

Coltan makes tantalum, and this grey-green metal, with its extreme stability at high temperatures, is an essential ingredient in high-end engineering of all kinds – especially aerospace and computing.

DRC holds about 80 per cent of the world’s coltan, 15 per cent of it beneath the unstable earth around Rubaya, which, at its peak, can produce up to 30 per cent of what global manufacturing consumes.

For around $5 a day, the miners here are at the centre of a very big business.

They’re also at the centre of the violent storm that Trump sought to end with a peace deal he brokered between DRC and Rwanda last year.

“They’ve spent a lot of time killing each other, and now they’re going to spend a lot of time hugging and holding hands and taking advantage of the United States of America,” he said in December.

In a telling nod to one of his motives for trying to bring peace, Trump added: “We’re going to take out some of the rare earth and the assets, and pay. And everybody’s going to make a lot of money.”

As part of the agreement, DRC president Felix Tshisekedi signed a “security for minerals” deal with the US. It is being challenged by his parliament, but, from his perspective, it might give his government an edge in trying to secure access to mineral resources – including the Rubaya mine, but also gold and timber operations – that rebel groups have controlled for decades with the help of neighbouring armies.

Article 2 of the deal said it would “strengthen opportunities for cooperation in security, defense, and protection of critical infrastructure, in safeguarding the integrity of the Democratic Republic of the Congo’s territory and strategic mineral reserves, in promoting regional stability, and in supporting peace and security across central Africa …”.

In Rubaya, before the mine collapse, the M23 rebels and their allies were netting at least $1m a month from taxing the output, which is sold in Rwanda and Burundi, where there is no coltan.

Miners clambered down shafts measuring between 100 and 200 metres deep, where temperatures soared and humidity hit close to 100 per cent.

Ventilation came from small household-style fans attached to duct pipes of the sort that is often seen emerging from bathroom extractors. Webs of cabling and hand-cut streams for washing the mineral webbed the landscape.

“It’s estimated that 10,000 to 11,000 people work here,” said Patrice, an M23-appointed mine manager, speaking before the collapse.

Michel – who emerged from a hole in the ground carrying white sacks of ore ready to be washed and searched for coltan – said he was “happy” with his wages and hoped to be able to buy a small shamba, a garden, close to Goma with his wife one day.

In the past, the mine was torn by fighting between militia and government forces, who would kill for control of such assets. For now, it remains outside the control of the central government, which has a well-earned reputation for corruption, while the national armed forces are among the worst human-rights abusers in the region.

There has been fierce fighting around Fizi, which is in South Kivu province many hours’ drive from Goma, as government forces have clashed with M23. There has been no sign of the US backing the government in this region.

But there are efforts by the government to sweeten the deal with the Trump administration and US mining houses. DRC officials recently travelled to Washington with a list of offers from various mines across the country.

At present, China dominates the DRC mining industry, having invested at least $11bn between 2008 and 2018.

“China now controls over half of global critical minerals production and an estimated 87 per cent of processing and refining,” states the Africa Centre for Strategic Studies. “China also produces nearly 70 per cent of rare earth minerals, manufactures 93 per cent of high-strength rare earth permanent magnets, and is responsible for 95 per cent of the necessary heavy processing of critical minerals.

“While China’s critical minerals strategy has emphasised its processing and refining capabilities, Beijing has diversified upstream by acquiring major African mining assets, including Botswana’s Khoemacau copper mine (2023), Mali’s Goulamina lithium mine (2024), and Tanzania’s Ngualla rare earth mine (2025).”

China has also built railways and roads and promised to improve infrastructure, with little regard for political probity or human rights issues.

But US companies have been encouraged to get back into the Congo region. US mining magnate Glencore is currently in talks to sell 40 per cent of its copper and cobalt operations to the US investment firm Orion.

But these mines are in southern Katanga province – far from North and South Kivu, where M23 rebel leaders have denounced the US deal and have used the minerals they control to expand their war. Most recently, they attacked Kisangani, hundreds of miles away, with modern drones.

The only slowing in the M23 mining operations since Trump’s deal with the government in the Congo has been due to the collapse of the Rubaya mine – a consequence of unregulated greed, not diplomacy.

This article has been produced as part of The Independent’s Rethinking Global Aid project