A viable mine  is  a function of  location ( Costs) and  grade/ value  and  tonage....

Tahara  was  sunk  not  because  of  its  diamond  grades and  value, but  because of  its location...... Everything.... even  toilet  paper  has an extra added  cost  when  its  in the  middle  of  nowhere.

If TAH  was 50kms from  yellowknife  like  SNO is,  they  would be a  very  profitable  operation. The  remote isolated  camps   have  all the  logistical problems  of  keeping  it  staffed, and  supplied allong  with the  limited  very  expensive ice  road-.

Costs   for  an equivelent operation that  has a  bedroom  community just  a 30 minuit  commute instead  of  an isolated work  camp, would  be  1 tenth of the  cost  to  operate....JMHO