Dear student,
1- The following are the major factors responsible for economic viability of a reserve:-
(1) The quality and quantity of mineral concentration in the ore.If concentration of mineral in ore is more it would be more economical to extract and would produce optimum output.
(2) The cost of extraction:- no matter what quality of mineral is present in the reserve aur how abundant is its quality quantity if the cost of extraction is high it will lead us to nowhere but our own deficit
(3) Location of mines and availability of transport.
2- The mineral deposits or reserves turn into a mine when it is found after geo technical investigation that the deposits are economically viable for mining.
Regards