I actually wrote the commemorative book (for Diamet and BHP) when they opened the Ekati diamond mine - the first - so I know a little about this subject:

1. BHP met every environmental demand, and cleared a huge number of social and economic hurdles, as well, before establishing that first mine.

2. The physical "damage" from the mine is contained to an area that you could walk around in an afternoon. There are no 70-square-kilometer toxic sewage lagoons lurking in wait for the next flight of migrating waterfowl.

3. The CO2 emissions directly related to the mine's operations probably come mostly from the passenger jet flights that bring employees to and from the very remote location. As for the mine and processing facility, it produces diamonds as its principal output, whereas the oil sands produce CO2 emissions as their principal output - on site and downstream.

Of course, in the real world, diamonds are the most useless commodity imaginable. You can fabricate perfectly serviceable "industrial diamonds" at a fraction of what it costs to dig real ones out of the ground. And gem diamonds are the biggest branding boondoggle in the history of market manipulation.

So, I grant that you might mount a legitimate argument over whether it's a good idea to carve up the wilderness purely for the pleasure of adorning pretty women in sparkles. But you can still mine diamonds without putting the habitability of planet earth at risk. The same cannot be said for the indiscriminate expansion of what is already the biggest CO2 point source in the country and could ultimately become the biggest point source on the continent, if not the planet.

Get a map of Alberta. How much "enviroment" are we talking about at the tar sands? Answer: Diddly Squat.

Why do the three diamond mines get free passes and the tar sands mines don't?

There are 3 working diamond mines in the NWT and three more are soon to start production.

How come gold and silver mines get free passes and the base metal and the coal mines don't?