The Green and the Black — William Meikle

A small group of industrial archaeologists head into the center of Newfoundland, investigating a rumor of a lost prospecting team of Irish miners in the late Nineteenth century. They find the remains of a mining operation, and a journal and papers detailing the extent of the miners' activities. But there is something else on the site, something older than the miners, as old as the rock itself. Soon the archaeologists are coming under assault, from a strange infection that spreads like wildfire through mind and body, one that doctors seem powerless to define let alone control. The survivors only have one option. They must return to the mine, and face what waits for them, down in the deep dark places, where the green meets the black.