By Damian Zane:

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 last 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 percent- 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

Over the past year, the M23 has made rapid advances across the mineral-rich east of DR Congo, taking areas where coltan – the ore from which tantalum is extracted – is mined.

Like scores of other armed groups operating in the area, the M23 began as an outfit defending the rights of an ethnic group perceived to be under threat. But as its territory has expanded, mining has become a crucial source of income, paying for fighters and weapons.

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.

They are part of a complex, and yet informal, network that sees the rocks removed from the ground using shovels, brought to the surface, crushed, washed, taxed, sold and then exported to be further purified and eventually smelted.

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