He setteth an end to darkness - That is, man does. The reference here is undoubtedly to the operations of mining, and the idea is, that man delves into the darkest regions; he goes even to the outer limits of darkness; he penetrates everywhere. Probably the allusion is derived from the custom of carrying torches into mines.
And searcheth out all perfection - Makes a complete search; examines everything; carries the matter to the utmost. The idea is not that he searches out all perfection - as our translation would seem to convey; but that he makes a complete and thorough search - and yet after all he does not come to the true and highest wisdom.
The stones of darkness - The last stone, says Herder, in the mining investigations in the time of Job; the corner or boundary stone, as it were, of the kingdom of darkness and night. Prof. Lee supposes that there is allusion here to the fact that stones were used as "weights," and that the idea is, that man had ascertained the "exact weight" of the gross darkness, that is, had taken an accurate admeasurement of it, or had wholly investigated it. But this solution seems far-fetched. Schultens supposes the center of the earth to be denoted by this expression. But it seems to me that the words "stone" and "darkness" are to be separated, and that the one is not used to qualify the other. The sense is, that man searches out everything; he perfectly and accurately penetrates everywhere, and examines all objects; "the stone" (אבן 'eben), that is, the rocks, the mines; "the darkness" (אפל 'ôphel), that is, the darkness of the cavern, the interior of the earth; "and the shadow of death" (צלמות tsalmâveth), that is, the most dark and impenetrable regions of the earth. So it is rendered by Coverdale: "The stones, the dark, and the horrible shadow."

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."

He setteth an end to darkness, (b) and searcheth out all perfection: the stones of darkness, and the shadow of death.
(b) There is nothing but it is compassed within certain limits, and has an end, but God's wisdom.

He setteth an end to darkness,.... Some understand this and what follows of God, who, by making the luminaries, has fixed the periods and revolutions of light and darkness, of day and night; or who has determined the times before appointed, for the discoveries of things in nature, as mines of gold, silver, and precious stones, how long they should lie in darkness, and then be brought to light, and who searches out the perfection of all things in nature; and makes them known to men, when he himself and his ways are not to be found out unto perfection by men; but rather this is to be understood of the miner that digs for the above metals, who, when he opens a mine, lets in natural light, or carries artificial light along with him, and so puts an end to the darkness which had reigned there before, even from the creation:
and searcheth out all perfection; searches thoroughly the mines he opens, and gets all he can out of them, and searches perfectly into the nature of the ore; he finds, and tries, and proves it, what it is, its worth and value:
the stones of darkness, and the shadow of death; searches and digs through them, to get at what he is seeking; or brings stones, precious stones, to light, which lay in darkness from the beginning, and in such places which were the shadow of death, and looked dismal and horrible, and even threatened with death, to get into and fetch them out: so spiritual miners, that search into the mines of the Scriptures, should not be discouraged with darkness and difficulties that may attend their search; but should continue it, in order to find out truths that have lain in darkness, more precious than gold and silver, and the richest gems; and such who search for them in like manner as miners do shall find them, Proverbs 2:4.

"Man makes an end of darkness," by exploring the darkest depths (with torches).
all perfection--rather, carries out his search to the utmost perfection; most thoroughly searches the stones of darkness and of the shadow of death (thickest gloom); that is, the stones, whatever they be, embedded in the darkest bowels of the earth [UMBREIT] (Job 26:10).

Perfection - Whatever is deeply wrought in the deepest caverns. Stones of darkness - The precious stones which lie hid in the dark bowels of the earth, where no living thing can dwell.