There is a good chance that inside your mobile phone is a miniscule amount of a metal that started its journey buried in the earth of eastern Democratic Republic of Congo, where a war is currently raging.

It may even be directly connected to the M23 rebel group that made global headlines this week.

The tantalum within your device weighs less than half of the average garden pea but is essential for the efficient functioning of a smartphone, and almost all other sophisticated electronic devices.

The unique properties of this rare, blue-grey, lustrous metal – including being able to hold a high charge compared to its size, while operating in a range of temperatures - make it an ideal material for tiny capacitors, which temporarily store energy.

It is also mined in Rwanda, Brazil and Nigeria but at least 40% - and maybe more – of the element's global supply comes from DR Congo and some of the key mining areas are now under the control of the M23.

The current wave of fighting has been going on for months, but the rebels grabbed attention with Sunday's assault on the vital trading and transport hub of Goma. The city, bordering Rwanda, is a regional centre for the mining business...

Last April, it seized Rubaya, the town at the heart of the country's coltan industry. Mineral extraction in this region is not in the hands of multinational conglomerates - instead thousands of individuals toil in open pits that honeycomb the landscape, or underground, in extremely unsafe and unhealthy conditions...

Once the M23 moved into Rubaya, the rebels established what a UN group of experts described as a "state-like administration", issuing permits to the diggers and traders and demanding an annual fee of $25 (£20) and $250 respectively. The M23 doubled the diggers' wages to ensure they would carry on working.

It runs the area as a monopoly making sure – through the threat of arrest and detention – that only its authorised traders are able to do business.

The M23 also charges a levy of $7 on each kilogramme of coltan. The UN group of experts estimated that as a result the M23 earns about $800,000 a month from coltan taxation in Rubaya. That money is almost certainly then used to fund the rebellion.

There is a question mark hanging over how the ore extracted from M23-controlled areas gets into the global supply chain.

Neighbouring Rwanda, which is seen as backing the M23, is at the centre of the answer, the UN experts say...

Rwandan President Paul Kagame has also dismissed the UN experts' reports, pouring scorn on their "expertise".

Much of the east of DR Congo has been blighted by conflict for many years, raising questions about who has been benefitting and whether armed groups are profiting from what is dug out of the ground there.

In order to highlight the issue and its connection to the smartphone industry, the Congolese government filed criminal complaints in France and Belgium at the end of last year against subsidiaries of the tech giant Apple, accusing it of using "conflict minerals".

Apple has disputed the allegation and pointed out that since early 2024, because of the escalating conflict and the difficulties of certification, it stopped sourcing tantalum, among other metals, from both DR Congo and Rwanda...