Just to add. The theory of the mine shutting down because it...

Just to add. The theory of the mine shutting down because it wasnt needed anymore seems ill advised when I keep reading this
"The mineral form of sodium hexafluoroaluminate, which is called cryolite, was mined at Ivigtût on the west coast of Greenland until the deposit was depleted in 1987"
https://en.wikipedia.org/wiki/Sodium_hexafluoroaluminate
The mine appears to have been depleted of cryolite but yet left a big lode of fluorite cryolite on the pit floor. Seems the previous miner even dug up tailings in the pier as suggested by another poster. But still left the fluorite cryolite for a reason not yet known.