LONDON Never a destination for the faint-hearted investor, the Democratic Republic of Congo is again worrying those betting on its mines and vast mineral wealth, as rebels battle government troops in the country's east.
Goma - a lakeside trade town at the centre of an eastern region that once exported significant quantities of tin, gold and tantalum, a metal used in electronics - has been taken by the M23 fighters, who are now progressing south.
The eastern Kivu regions had seen exports tumble even before the recent months of fighting, as tighter controls on companies' supply chains hit the mostly artisanal mining operations. Without tags to certify origin, buyers like electronics powerhouses Apple or Intel steer clear of the region's metals.
Industry sources and analysts say the fighting - in an area that has seen recurring ethnic strife - is unlikely to spread far beyond the region, certainly not as far south as the major copper mines of Katanga, a region more than 1,000 kilometers (625 miles) south of Goma that has been the heart of Congo's mining industry.
"This is not national. You can't correlate it with (the civil war of) 2003; it is a different conflict," said Mark Bristow, CEO of Randgold, which works in Mali and Ivory Coast and is developing the Kibali project in Congo's northeast.
"Without wanting to downplay the seriousness of this - and it is serious - it is fairly well defined to the region. We don't see it spreading, and it is very encouraging the population at large is clear about (wanting) national unity."
But campaigners and industry analysts say the unrest will set back efforts to boost legitimate mining in the east, and to clean up Congo's tarnished reputation.
Unchecked progress towards Bukavu - 200 km by road from Goma, south along Lake Kivu - will bring the rebels closer to Canadian miner Banro's Twangiza operation, Congo's first new gold mining project for more than half a century, and hailed at its debut last year as a symbol of revival in a war-scarred region.
Banro's shares have lost more than a quarter of their value since reports of fighting began to emerge this month, though the company has said operations are normal.
Congo is the world's 24th-largest gold producer, according to GFMS.
Still recovering from years of under-investment in its mining infrastructure, Congo attracts most attention for its vast reserves of copper. It produced 435,400 metric tons last year, according to metals research group GFMS, making it the world's 10th largest producer of the metal.
Congo's major international copper miners, from Freeport McMoRan to Glencore and ENRC, operate in Katanga, and have soothed investors by emphasizing their distance from the fighting, hundreds of kilometers away.
Company officials from the major miners told Reuters they were monitoring the situation, but all said their export routes and production were unaffected.
Canadian-listed Alphamin is drilling in the Bisie tin deposit in North Kivu, one of the biggest in the region and a project that has long been fought over by the army and rebels. Alphamin did not respond to a request for comment.
BAG AND TAG
The main impact, industry analysts say, is likely to be on longer-term efforts to bring "bag and tag" initiatives to the volatile east - allowing electronic giants like Apple and other buyers to come back without falling foul of the Dodd Frank law.
Under rules only finalized this year, the law requires U.S. companies to ensure their supply does not come from areas controlled by armed groups or corrupt soldiers.
As a result of concerns over conflict minerals, Congo made up only 1.5 percent of the global tin market last year - down from 4 percent in 2008.
But the region has pushed ahead with initiatives like the cooperative-operated Kalimbi mine in South Kivu, which has been tagging its tin to secure legitimate - and better priced - sales.
"Considerable efforts are being made in the region to set up responsible, conflict-free supply chains. We need to make sure this progress isn't reversed by the M23's advance," said Annie Dunnebacke, a senior campaigner at Global Witness.
Fighting in the region has long been linked to the plundering of its mineral wealth - illegally mined tin, gold and coltan, shorthand for an ore that is mined for tantalum.
United Nations investigators have said that rebel groups and rogue elements in the army have smuggled minerals abroad, circumventing government mining and export bans on metals. Much "conflict" metal is shipped through Rwanda, experts say.
Though only a small portion of the world's tantalum reserves are in central Africa - less than 10 percent according to research firm Roskill - a large portion of tantalum comes out of the conflict region. Roskill estimates conflict tantalum made up 23 percent of primary supply in 2011.
(Additional reporting by Edward Stoddard in Johannesburg; Editing by Will Waterman)