Nicene and Post-Nicene Fathers, Ser. II, Vol I:
The Life of Constantine with Orations of Constantine and Eusebius.: Chapter VIII

p. 566 Chapter VIII.—That God bestows an Abundant Supply of whatever is suited to the Wants of Man, and ministers but sparingly to his Pleasures; in Both Cases with a View to his Advantage.

Let what has been said suffice to prove that nothing exists without reason and intelligence, and that reason itself and providence are of God. It is he who has also distributed the metals, as gold, silver, copper, and the rest, in due proportion; ordaining an abundant supply of those which would be most needed and generally employed, while he dispensed those which serve the purposes merely of pleasure in adornment of luxury with a liberal and yet a sparing hand, holding a mean between parsimony and profusion. For the searchers for metals, were those which are employed for ornament procured in equal abundance with the rest, would be impelled by avarice to despise and neglect to gather those which, like iron or copper, are serviceable for husbandry, or house-building, or the equipment of ships; and would care for those only which conduce to luxury and a superfluous excess of wealth. Hence it is, as they say, that the search for gold and silver is far more difficult and laborious than that for any other metals, the violence of the toil thus acting as a counterpoise to the violence of the desire. And how many instances might still further be enumerated of the workings of that Divine Providence which, in all the gifts which it has so unsparingly conferred upon us, plainly urges us to the practice of self-control and all other virtues, and leads us away from unbefitting covetousness! To trace the secret reasons of all these things is indeed a task which exceeds the power of human faculties. For how can the intellect of a frail and perishable being arrive at the knowledge of perfect truth, or apprehend in its purity the counsel of God from the beginning?