You have to understand that there is not one body of ore at Windfall. Gold is hosted in a series of 'lenses' , you could think of them as wide veins and they are not connected.

This is what makes it so difficult to come up with a resource estimate and why they want to try to drill from underground to get a better handle on deposits. Quebec has some of the best miners in the world with experiance at exploting this kind of mineralization but it's not inexpensive mining, nothing at all like bulk mining of low grade ore.