Agricola - De Re Metallica (1556).

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For over 180 years with its 422 illustrations, THIS was THE book on mining and assaying.

The first 34 illustrations are about the ore veins his miner friends were exploiting.


You can download your copy here:

ia800201.us.archive.org/27/items/georgiusagricola00agririch/georgiusagricola00agririch.pdf

Georg Bauer (or Pawer) was born at Glauchau in Saxony in 1494 just two years after Columbus "sailed the ocean blue."

Many authors of the time "Latinised" their names in their published works. Bauer means ‘peasant’ or ‘farmer’ in German so the Latin noun for farmer, Agricola, was used by his contemporaries and he is known to history as Georgius Agricola.

Agricola entered the University of Leipsic at the age of twenty, and after about three and one-half years' attendance there gained the degree of Baccalaureus Artium. In 1518 he became Vice-Principal of the Municipal School at Zwickau, where he taught Greek and Latin. In 1520 he became Principal, and among his assistants was Johannes Forster, better known as Luther's collaborator in the translation of the Bible.

In 1522 he removed to Leipsic to become a lecturer in the University under his friend, Petrus Mosellanus, at whose death in 1524 he went to Italy for the further study of Philosophy, Medicine, and the Natural Sciences. Here he remained for nearly three years, from 1524 to 1526.

In 1526 Agricola returned to Zwickau, and in 1527 he was chosen town physician at Joachimsthal. This little city in Bohemia is located on the eastern slope of the Erzgebirge, in the midst of the then most prolific metal mining district of Central Europe. Thence to Freiberg is but fifty miles, and the same radius from that city would include most of the mining towns so frequently mentioned in De Re Metallica - Schneeberg, Geyer, Annaberg and Altenberg and not far away were Marienberg, Gottesgab, and Flatten.

Joachimsthal was a booming mining camp, founded but eleven years before Agricola's arrival, and already having several thousand inhabitants. According to Agricola's own statement, he spent all the time not required for his medical duties in visiting the mines and smelters, making drawings and reading up in the Greek and Latin authors all references to mining, and in association with the most learned among the mining folk. Among these was one Lorenz Berman, whom Agricola called the "learned miner."

De Re Metallica  was published just forty years after Gutenberg's first book was printed.

This is the July 1, 1912 Hoover Translation - translated by the future US President Herbert Clark

Hoover, who was a mining engineer by profession, and his wife Lou Henry, a geologist and Latinist.

Lou had seen a copy of De re metallica in London in 1905 and, for the next five years, she and her husband worked on translating it.

Nearly every detail of the works Agricola observed is clearly covered in the text and his illustrations.

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Book 7 is about assaying:

Agricola Book 7 - Assaying.

SINCE the Sixth Book has described the iron tools, the vessels and the machines used in mines, this Book will describe the methods of assaying ores; because it is desirable to first test them in order that the material mined may be advantageously smelted, or that the dross may be purged away and the metal made pure.
Although writers have mentioned such tests, yet none of them have set down the directions for performing them, wherefore it is no wonder that those who come later have written nothing on the subject.

By tests of this kind miners can determine with certainty whether ores contain any metal in them or not ; or if it has already been indicated that the ore contains one or more metals, the tests show whether it is much or little ; the miners also ascertain by such tests the method by which the metal can be separated from that part of the ore devoid of it ; and further, by these tests, they determine that part in which there is much metal from that part in which there is little.

Unless these tests have been carefully applied before the metals are melted out, the ore cannot be smelted without great loss to the owners, for the parts which do not easily melt in the fire carry the metals off with them or consume them. In the last case, they pass off with the fumes ; in the other case they are mixed with the slag and furnace accretions, and in such event the owners lose the labour which they have spent in preparing the furnaces and the crucibles, and further, it is necessary for them to incur fresh expenditure for fluxes and other things.

Metals, when they have been melted out, are usually assayed in order that we may ascertain what proportion of silver is in a centumpondium of copper or lead, or what quantity of gold is in one libra of silver ; and, on the other hand, what proportion of copper or lead is contained in a centumpondium of silver, or what quantity of silver is contained in one libra of gold. And from this we can calculate whether it will be worth while to separate the precious metals from the base metals, or not.

Further, a test of this kind shows whether coins are good or are debased ; and readily detects silver, if the coiners have mixed more than is lawful with the gold ; or copper, if the coiners have alloyed with the gold or silver more of it than is allowable. I will explain all these methods with the utmost care that I can.

The method of assaying ore used by mining people, differs from smelting only by the small amount of material used. Inasmuch as, by smelting a small quantity, they learn whether the smelting of a large quantity will compensate them for their expenditure ; hence, if they are not particular to employ assays, they may, as I have already said, sometimes smelt the metal from the ore with a loss or sometimes without any profit ; for they can assay the ore at a very small expense, and smelt it only at a great expense.

Both processes, however, are carried out in the same way, for just as we assay ore in a little furnace, so do we smelt it in the large furnace. Also in both cases charcoal and not wood is burned. Moreover, in the crucible when metals are tested, be they gold, silver, copper, or lead, they are mixed in precisely the same way as they are mixed in the blast furnace when they are smelted. Further, those who assay ores with fire, either pour out the metal in a liquid state, or, when it has cooled, break the crucible and clean the metal from slag ; and in the same way the smelter, as soon as the metal flows from the furnace into the forehearth, pours in cold water and takes the slag from the metal with a hooked bar. Finally, in the same way that gold and silver are separated from lead in a cupel, so also are they separated in the cupellation furnace.

It is necessary that the assayer who is testing ore or metals should be prepared and instructed in all things necessary in assaying, and that he should close the doors of the room in which the assay furnace stands, lest anyone coming at an inopportune moment might disturb his thoughts when they are intent on the work. It is also necessary for him to place his balances in a case, so that when he weighs the little buttons of metal the scales may not be agitated by a draught of air, for that is a hindrance to his work.

Now I will describe the different things which are necessary in assaying, beginning with the assay furnace . . .

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The crucibles differ in the materials from which they are made, because they are made of either clay or ashes ; and those of clay, which we also call "earthen," differ in shape and size. Some are made in the shape of a moderately thick salver (scorifiers), three digits wide, and of a capacity of an uncia measure ; in these the ore mixed with fluxes is melted, and they are used by those who assay gold or silver ore. Some are triangular and much thicker and more capacious, holding five, or six, or even more unciae ; in these copper is melted, so that it can be poured out, expanded, and tested with fire, and in these copper ore is usually melted.

The cupels are made of ashes ; like the preceding scorifiers they are tray-shaped, and their lower part is very thick but their capacity is less. In these lead is separated from silver, and by them assays are concluded.

Inasmuch as the assayers themselves make the cupels, something must be said about the material from which they are made, and the method of making them. Some make them out of all kinds of ordinary ashes ; these are not good, because ashes of this kind contain a certain amount of fat, whereby such cupels are easily broken when they are hot. . . .

If ashes of beech or similar wood are not to be had, the assayer makes little balls of such ashes as he can get, after they have been cleared of impurities in the manner before described, and puts them in a baker's or potter's oven to burn, and from these the cupels are made, because the fire consumes whatever fat or damp there may be. As to all kinds of ashes, the older they are the better, for it is necessary that they should have the greatest possible dryness.

For this reason ashes obtained from burned bones, especially from the bones of the heads of animals, are the most suitable for cupels, as are also those ashes obtained from the horns of deer and the spines of fishes. Lastly, some take the ashes which are obtained from burnt scrapings of leather, when the tanners scrape the hides to clear them from hair. Some prefer to use compounds, that one being recommended which has one and a half parts of ashes from the bones of animals or the spines of fishes, and one part of beech ashes, and half a part of ashes of burnt hide scrapings. From this mixture good cupels are made, though far better ones are obtained from equal portions of ashes of burnt hide scrapings, ashes of the bones of heads of sheep and calves, and ashes of deer horns. But the best of all are produced from deer horns alone, burnt to powder ; this kind, by reason of its extreme dryness, absorbs metals least of all. Assayers of our own day, however, generally make the cupels from beech ashes. These ashes, after being prepared in the manner just described, are first of all sprinkled with beer or water, to make them stick together, and are then ground in a small mortar. They are ground again after being mixed with the ashes obtained from the skulls of beasts or from the spines of fishes ; the more the ashes are ground the better they are.

Some rub bricks and sprinkle the dust so obtained, after sifting it, into the beech ashes, for dust of this kind does not allow the hearth-lead to absorb the gold or silver by eating away the cupels. Others, to guard against the same thing, moisten the cupels with white of egg after they have been made, and when they have been dried in the sun, again crush them ; especially if they want to assay in it an ore or copper which contains iron. Some moisten the ashes again and again with cow's milk, and dry them, and grind them in a small mortar, and then mould the cupels. In the works in which silver is separated from copper, they make cupels from two parts of the ashes of the crucible of the cupellation furnace, for these ashes are very dry, and from one part of bone-ash. Cupels which have been made in these ways also need to be placed in the sun or in a furnace ; afterward, in whatever way they have been made, they must be kept a long time in dry places, for the older they are, the dryer and better they are.

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The colour of the fumes which the ore emits after being placed on a hot shovel or an iron plate, indicates what flux is needed in addition to the lead, for the purpose of either assaying or smelting.
If the fumes have a purple tint, it is best of all, and the ore does not generally require any flux whatever.
If the fumes are blue, there should be added cakes melted out of pyrites or other cupriferous rock;
if yellow, litharge and sulphur should be added;
if red, glass-galls and salt;
if green, then cakes melted from cupriferous stones, litharge, and glass-galls;
if the fumes are black, melted salt or iron slag, litharge and white lime rock.
If they are white, sulphur and iron which is eaten with rust;
if they are white with green patches, iron slag and sand obtained from stones which easily melt;
if the middle part of the fumes are yellow and thick, but the outer parts green, the same sand and iron slag.

The colour of the fumes not only gives us information as to the proper remedies which should be applied to each ore, but also more or less indication as to the solidified juices which are mixed with it, and which give forth such fumes.
Generally, blue fumes signify that the ore contains azure ; yellow, orpiment ; red, realgar ; green, chrysocolla ; black, black bitumen ; white, tin18; white with green patches, the same mixed with chrysocolla ; the middle part yellow and other parts green show that it contains sulphur.
Earth, however, and other things dug up which contain metals, sometimes emit similarly coloured fumes.

If the ore contains any stibium, then iron slag is added to it;
if pyrites, then are added cakes melted from a cupriferous stone and sand made from stones which easily melt.
If the ore contains iron, then pyrites and sulphur are added ; for just as iron slag is the flux for an ore mixed with sulphur, so on the contrary, to a gold or silver ore containing iron, from which they are not easily separated, is added sulphur and sand made from stones which easily melt.

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Now let us consider which is more suitable for each ore, or, if neither is suitable, by what other method in one way or another we can assay it.

We justly begin with a gold ore, which we assay by both methods, for if it is rich and seems not to be strongly resistant to fire, but to liquefy easily, one centumpondium of it (known to us as the lesser weights),²⁷

"This method of proportionate weights for assay charges is simpler than the modern English "assay ton," both because of the use of 100 units in the standard of weight (the centumpondium), and because of the lack of complication between the Avoirdupois and Troy scales. For instance, an ore containing a libra of silver to the centumpondium would contain i /zooth part, and the same ratio would obtain, no matter what the actual weight of a centumpondium of the "lesser weight" might be. To follow the matter still further, an uncia being 1/1,200 of a centumpondium, if the ore 'ran one "uncia of the lesser weight" to the "centumpondium of the lesser weight," it would also run one actual uncia to the actual centumpondium ; it being a matter of indifference what might be the actual weight of the centumpondium upon which the scale of lesser weights is based. In fact Agricola's statement (p. 261) indicates that it weighed an actual drachma.

We have, in some places, interpolated the expressions "lesser" and "greater" weights for clarity.

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Where is Zwickau?