Ann: Quarterly Activities Report SEP 2009 , page-22

UFX

you say

"When a mining face is blasted, rock is fractured and broken along the whole height of the stope"

actually it is quite possible to be selective about the material that is blasted out of a mining face by using carefully determined drilling patterns with uncharged holes to produce what are called free faces

there are several other techniques that support selective blasting such as using exploders that have programmed delays, short delay detonators, angular blastholes, artificial openings (usually called "cuts"), sequential firing, detecting planes of weakness, step type stoping ... there are other techniques

these blasting techniques require lots of skill and experience and that's why top gun airleg operators are highly paid