I'd think that the Greenland authorities would be pretty angry...

I'd think that the Greenland authorities would be pretty angry about a turn of events such as you mention but they may be helpless. Other mines haven't succeeded in Greenland. Wouldn't the Danish Government prefer to have income for Greenland in order to alleviate their subsidisation of Greenland albeit probably not overburdensome? What, if anything, could these governments do to stop manipulation by a large investor? As a matter of fact, these days, Glencore is not a large investor.

Agreed that Glencore may prefer not to have this one built for a very long time if their aim is to keep zinc in high demand and therefore prices up.

A thought - a company the size of a Glencore (as an example) may be able to use leverage against large buyers of zinc who also buy large quantities from the same company of other necessary commodities. Would this deter investors? I would think that large buyers such as those controlled by governments would be smarter than the average bear and be able to counter such a game?

The head breaks!!