Gregory the Dialogist

Iron is taken out of the earth. And the stone being melted with heat is turned into brass. Moreover, we are to consider that there are some whom Almighty God by His secret counsel preserving in innocency from their very beginnings promotes to the topmost heights of virtuous attainments, that, as their age increases, both numerousness of years and loftiness of merits should simultaneously advance in them. But others abandoning in their outset He suffers to go with bad habits fermenting by headlong ways. …

Morals on the Book of Job, Book XVIII ↗

Thomas Aquinas

As to iron he says, "Iron is taken from the earth," because it is found in the earth not yet refined, as it were. As to bronze he says, "and stone," with which one finds a gas proportioned to its nature is mixed, "released by heat," of great intensity, "changed to bronze," when what is found there of the nature of bronze is made aqueous by the heat of fire.

Commentary on Job ↗