More than a decade ago, Canadian miners prospecting for diamonds in western Greenland saw on the horizon a huge white hump.

They called it White Mountain and soon discovered it was a deposit of anorthosite, a salt-and-pepper color mineral used in paints, glass fibers, flame retardants and other industries. The same mineral creates a ghostly glow on the moon’s surface.

The White Mountain deposit proved to be several miles long and several miles wide, and “only God knows how deep it goes,” said Bent Olsvig Jensen, the managing director of Lumina Sustainable Materials, the company mining the area.

Lumina is backed by European and Canadian investors, but Mr. Jensen said it wasn’t easy to turn the deposit into a mountain of cash.

“You cannot do exploration all year round; you are in the Arctic,” he explained.

He told of fierce winds grounding helicopters and knocking out communications, pack ice blocking ships and temperatures dropping to such a dreadful low — sometimes minus 40 degrees Fahrenheit — that the hydraulic fluid powering the company’s digging machines “becomes like butter.”

Sitting in Lumina’s humble offices in Nuuk, Greenland’s capital, with wet snow flakes scissoring down outside the windows, Mr. Jensen brought a dose of sobriety to all the talk of Greenland as the land of incalculable mineral riches. He noted that though the island has dozens of exploratory projects, there are only two active mines: his and a small gold operation.