He cutteth out rivers among the rocks; and his eye seeth every precious thing. He cutteth out rivers among the rocks - He cuts canals, adits, etc., in the rocks, and drives levels under ground, in order to discover loads or veins of ore. These are often continued a great way under ground; and may be poetically compared to rivers, channels, or canals.
His eye seeth every precious thing - He sinks those shafts, and drives those levels, in order to discover where the precious minerals lie, of which he is in pursuit.