Five thousand diggers pack tightly together at the bottom of a crater in southeastern DR Congo, swinging hammers and picks to prise chunks of speckled blue-gold ore from the earth. The huge pit in Shabara, about 45 kilometres (30 miles) from Kolwezi, is home to cobalt - a strategic metal found in abundance in the impoverished central African nation. But it's also emblematic of a headache. The mining has been carrying on for years in flagrant violation of DRC laws and in defiance of the site's owner, a subsidiary of mining and commodities giant Glencore.