In the walls, floor and ceilings of squelching tunnels deep beneath a County Tyrone hill lie minerals that may be worth more than $20bn (£15bn), mostly gold and silver but also antimony, bismuth, cobalt, copper and tellurium. Such are the riches that developers claim could be unearthed at Curraghinalt in rural Northern Ireland. Yet the plan to extract them is so bogged down in government bureaucracy that it’s unclear if the mine will produce an ounce of gold.