Adam Clarke on Job 28:3

He setteth an end to darkness - As it is likely Job still refers to mining, the words above may be understood as pointing out the persevering industry of man in penetrating into the bowels of the earth, in order to seek for metals and precious stones. Even the stones that lay hidden in the bowels of the earth he has digged for and brought to light, and has penetrated in directions in which the solar light could not be transmitted; so that he appears to have gone to the regions of the shadow of death. Mr. Good translates: "Man delveth into the region of darkness; and examineth, to the uttermost limit, the stones of darkness and death-shade."