From a 16th century metallurgy text
At some point in the past, I have mentioned the very famous book called The Pirotechnica by Vannoccio Biringuccio. (It is available from Dover Publications.) This book was published in 1540 and is the classic work of metallurgy - the engineering discipline of refining metals. Before his death, Biringuccio was appointed head of the papal foundry - a curious position, until one remembers that churches need bells! - and one which suggests the good relation of the Church to engineering.
I will quote an important excerpt from the preface concerning the location or ores. It is interesting because of the spiritual dimension - and because it suggests something very insightful about the use of "necromancy" (magic) which I have not heard anyone advance elsewhere... please read it and see what it suggests to you...
...I do not believe that one man, however strong and careful he may be, has enough strength to go about minutely examining a single mountain that might contain ore, much less all the mountains of one or more provinces. Some, because they know of this difficulty, say that they make use of necromancy. Since I consider this a fabulous thing and have no information of what it may be, I intend neither to praise nor to damn it, and yet if what they say they do were indeed true, it would be a very useful thing. However, I wish these necromancers would tell me why they do not use their art after they have found the ore and do also for the middle and the end what they do for the beginning; that is, use their art for excavating the ore and reducing it to smelted material and to the purity of its separation. Without doubt it can be believed that if they have the power to do one of the said things, they also have the power to do the others, but such operations are so fearful and horrible that they neither should nor could be practiced, nor would all men wish to do so. Such a thing is not well known, and I have never heard that it is practiced. The principal reason why it must be believed that such practices are abandoned in this part of the work is that whenever the excavation of a mine is begun, it is customary first to seek the grace of God, so that He may intervene to aid every doubtful and difficult effort; and in place of this one would be seeking the aid of the devils of hell. Whence, in order to discover ores, I think it better to abandon the way of bestial and fearless men and to choose the way of using the signs that are exhibited to us through the benignity of Nature, founded on truth and approved by all experts because of their experience, which, as is evident, does not consist of words or promises of incomprehensible and vain things.