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Renaissance "Metallic gold is used by the alchemists to prepare a liquid that they affirm will restore youth when drunk." Agricola, De natura fossilium, 1546     The advanced technology utilized in gold mining and placering, and described by the Renaissance writers, was all developed during the High and Late Middle Ages and are briefly mentioned in the previous chapter. Blasting techniques for breaking rock and ore using black powder seem to have been experimented with in the late years of the Renaissance, but explosives did not find widespread use in mining until modern times. Theories of the origin of gold deposits in the Renaissance  In the dialogue of Bergwerk-und Probierbiichlein (written about 1497 by Calbus (Ulrich Riilein von Kalbe), learned doctor and onetime burgomaster of Freiberg in Saxony) the master miner Daniel (probably the first mining geologist) explains to his apprentice Knappius the nature and origin of mineral deposits. In the translation by Sisco and Smith (1949, p. 19) we read:    We see in this account of the origin of ores a somewhat muddled version of the views of the Aristotelians, the alchemists, and the astrologers. Reading further in the Bergbiichlein we learn about methods of prospecting for veins, and in the fifth chapter we have an exposition on gold ore. From the translation of Sisco and Smith (1949, p. 39) we read: On Gold Ore "Gold, however, according to the opinion of the philosophers, is made from the very finest sulfur -so thoroughly purified and refined in the earth through the influence of Heaven, especially the Sun, that no fattiness is retained in it that might be consumed or burnt by fire, nor any volatile, watery moisture that might be vaporized by fire-and from the most persistent quicksilver, so perfectly refined that the pure sulfur is not impeded in its influence on it and can thus penetrate and colour it from the outside to its very core with its persistent shade of citrine. And thus the two, sulfur and quicksilver, being the mineral matter, are joined into a metallic body in the most powerful and enduring union through the influence of Heaven, delegated to the Sun, and through the fitness of the location, through which the mineral exhalations of sulfur and quicksilver wind and drive and break their way. And such union cannot be dissolved even by the most violent and most powerful effort of fire. Gold occurs in different ways. Some, in ordinary river sand, some under the overburden near swamps, some in pyritic deposits, some, as the native metal, in stringers and veins, and some in various ores and alteration products contained in veins and stringers, whether these are schists, or black, brown, grey, blue, or yellow alteration products, or clayey ores. The gold generated in river sand is the purest and most exalted kind because its matter is most thoroughly refined by the flow and counter-flow of the water and also because of the characteristics of the location where such gold is found, that is, the orientation of the river in which such placer gold is made. The most suitable location for a river is one between mountains in the north and a plain in the south or west. And the most suitable direction of the current is from east to west. The next best is from west to east, with mountains located as described before. The third best is from north to south, with mountains in the east. But the worst, as far as the generation of gold is concerned, is from south to north if high mountains rise in the west. The possible directions of the flow of water are as manifold according to the quarters of the earth, as those of the strike of veins, which was described earlier in the chapter on silver ores. And each direction is judged better or worse in the measure as it approaches or deviates from what has been said above.  Disregarding some rather fanciful ideas such as the influence of Heaven, we have in this description a relatively modern account of the occurrence of gold. Calbus credits Albertus Magnus with some of the ideas in his narrative and follows him in considering that alluvial gold accretes in situ in streams. The reference to the association of tourmaline, especially the very fine crystalline type as opposed to the coarse crystalline variety, is remarkable because I have found this fact to be true in many auriferous deposits personally investigated.  "Because I cannot say that I have seen with my own eyes mountains which contain gold ores or places where the practice of such work is carried on, I shall tell you only what I have been told by trustworthy persons as I carefully tried to understand, or else what I have learned by reading various authors. From these I have gathered that it is true that most of this metal is found in Scythia and in those regions called oriental, perhaps because the sun seems to shine forth with greatest vigour in those places. Among these it is said that the Indies hold first place, particularly those islands which as we hear are called Peru, recently discovered by the naval armada of the sacred King of Portugal and of His Majesty the Emperor, and still other places. Also, gold is found in many localities in Europe such as Silesia, many parts of Bohemia, Hungary, in the Rhine, and in the Apsa. Pliny says that it is also found in Asturia and in Lusitania and that the Romans extracted twenty-three pounds every year.  Such gold-bearing pyrites is found in some places as bedded deposits that extend through the rock as a complete stratum; according to regional custom, these are sometimes called horizontal veins. Others occur in the form of [fissure] veins, that is, as upright veins that have hanging and footwalls. The flat-lying pyritic deposits are very low in gold content because the influence of Heaven, owing to the lack of fitness of the position, can exert itself but little. The gold-bearing pyrites that occur in veins are supposed to increase in richness and gold content in the measure as the country rock of the hanging and footwalls of a vein becomes finer and richer. And depending also on whether or not the strike and outcrop of a vein are in the right direction and whether a vein encounters other stringers that enrich it, as was explained in the chapter on silver ores, the occurrence will vary in quality and gold content. Of the gold that is generated in other than pyritic veins some is found as native gold attache d to the rock, some in yellow clay, some in a brown, fine alteration product, and some finally mixed and worked in with quartz. Where this brown alteration product occurs as a vein, the prospects are very good; because, with added ore from hanging-wall stringers, it will become very rich at depth.  As I told you before gold is also found in the sands of various rivers, as in Spain in the Tagus, in Thrace in the Hebrus, in Asia in the Pactolus and the Ganges, in various rivers in Hungary, Bohemia, and Silesia and in Italy in the Ticino, the Adda, and the Po. It is not, however, found throughout their beds but only in particular places, where in certain bends there is some bare gravel, or where the water in times of flood leaves a certain sandy sediment in which gold is mixed in tiny particles like scales or even smaller than a grain of flour. In the winter when the floods pass they take and carry them almost beyond the bed of the river so that when the waters return to their normal state they cannot easily take them away again, and thus they form mounds." The mention of the association of gold and pyrite and also of contaminated sulfur in the pyrite is of interest. The contaminated sulfur, or "bastard" sulfur as many alchemists referred to the substance, is none other than arsenic, and the type of pyrite meant is probably arsenopyrite. The remark that the stratiform (massive) pyrite deposits are low in gold is a general truism; why, we do not yet know. Mention of the brown alteration product (limonite) and the yellow clay (scorodite) suggests that Vannoccio Biringuccio was aware that some oxidized gold veins are enriched at depth, often immediately below the gossan. This mention is one of the first detailed references in the modern literature on gold to the secondary enrichment processes in auriferous deposits. Continuing with the origin of placer gold we read further in the translation by Smith and Gnudi (1959, p. 30) "But now let us cease speaking of these things because here perhaps you or someone else might like to know why such gold is carried by the water into these river sands and woods and whether indeed it is produced therein. I have often thought about this, greatly marvelling, particularly in regard to the Ticino, the Adda, and the Po, but the reason is not clear to me, since although I told you before that great floods of water carry it to where it can be extracted, there is no gold mine near those places or even one of any other metal that I know of. I am also confused because I have seen several authors who believe that it is generated in the very place where it is found; and if this were true it would not be true that the waters had brought it. But that it is generated there seems to me a very difficult thing to comprehend, since I do not understand whether it is produced by the innate properties of the waters or of the earth or indeed of the heavens, for it appears reasonable that if the cause were any of t hese it would be found everywhere in the bed of a given river, and, seeking, one would find it everywhere at all times. If the influence of the heavens is the powerful cause that produces gold, it seems to me that it would necessarily have to operate instantaneously because it is not possible otherwise to perceive the order that Nature uses in generating metals. It would have to produce it first in the open in a place where there is a continuous flow of water, and then it would have to have the power to remove the earthy materials from place to place and also to mix with it the greatly different qualities of cold and humidity. And even if this composition and order begun by the waters of the river should not change, it seems to me that the rains or floods which pass over it would completely soften, break, and entirely spoil anything that might be conceived therein. Furthermore, if this material is generated there, I wish to be told why it is generated only in these and not in other places, and why silver, co pper, lead, or one of the other metals similar to gold is not likewise generated in a similar manner, for these substances are perhaps even easier for Nature to form than gold because of the many concordances and ultimate perfections that gold requires. Moreover, in many places in the countryside near Rome particles of iron are found in the sands of several small rivers and I would like to know why this also is conceded only to certain particular parts of the river and not to all parts. For these reasons and visible phenomena it seems more probable that gold is carried by the water than that it is generated there. Nor does our dilemma help us to ascertain the truth. For, speaking just between ourselves-not with firm conviction, but only to tell you what I think- I say that I incline toward either of two theories. Of these one is that this phenomenon occurs only in very large rivers which receive much water from springs, streams, and other rivers and so it often happens that, with the melting of snows or the coming of heavy rains, they wash the banks and the slopes of near-by mountains, in which it may be that there is earth that, by its own particular nature, contains the substance of gold; or else the ores are located in some peak or surface where men have not yet taken the trouble to go or where access is difficult, and may then be exposed to insemination by the sun or by the coldness of the snows or by the waters, and broken up because in heavy rains anything is easily worn away and carr ied off to the rivers. Alternatively it might be that such earth is inside the nearby mountains or indeed in the same principal stream that has its bed hidden from our eyes. Since it is never dried up or free from continuously running water, it is not strange that in so many centuries the true origin and knowledge of such a thing should not be understood by those who live near by. But however it may be, in the end the truth is that gold is found in the sands of many rivers, particularly, according to my information, in those mentioned above. Therefore, if I have marvelled at this thing, I deserve to be excused, because where it is impossible to understand the certain cause of things either by reason or by direct observation, doubt always exists and new reasons for wonder are born. But I marvel even more greatly at what I have heard told many times as the truth by various persons: that in several places in Hungary at certain times the purest gold springs from the earth like grass and wraps itself like the stems of convolvulus around the young dry shoots. It is about as thick as a piece of string and about fourdita long or even apalmo. Apparently Pliny in the thirty-third book of his Natural history refers to this or a similar thing when he speaks of ores, incidentally referring to the fact that in his time this same thing occurred in Dalmatia. If what is said be true, then indeed would the farmers in the fields reap the fruits of celestial instead of terrestrial sowing, and they would be considered blessed, since such previous and pleasing fruits would be produced by God, by the heavens, or by Nature, without any labour or skill on their part. This would indeed be a unique grace, since among all the vast amount of earth and number of possessions that are cultivated by living creatures, none but these regions are worthy of such a harvest. What shall I say of what Albertus Magnus writes in his work De Mineralibus, where he says that he has seen gold generated in the head of a dead man? He says that when this was dug up by chance and found to be extraordinarily heavy, it was seen to be full of very fine sand. Because of its weight those who saw it thought that it was metal and by experimenting finally found it to be of the purest gold. It seems to me that his words have no other significance than that the ready disposition of the thing and the great influence of the heavens had generated this precious metal. Since I heard it thus, I wanted to pass it on to you. To tell the truth it is not easy to believe this, and certainly to me it seems incredible, yet considering who tells of it and thinking how great are the forces of superior causes and of Nature, we can receive it, having faith and respect for the learning to those who relate it, since by ourselves we lack full understanding of the causes of things."  "For this reason I tell and advise you that I believe the best thing to do is to turn to the natural gold and silver that is extracted from ores rather than that of alchemy (i.e. the transmutation of base metals into gold), which I believe not only does not exist but also, in truth has never been seen by anyone, although many claim to have seen it." The astral theory that gold is found in greatest abundance in those lands (between the tropics) where the sun shines with greatest vigour had many ramifications in medieval and Renaissance history and indeed in more modern history. For Examples: geographical exploration during the fifteenth and sixteenth centuries was stimulated in part by the search for gold, and the tropics were considered the most favourable zones in which to find the precious metal, as witnessed by the statement of Columbus recorded in his log book as he approached Watling Island in the Caribbean in 1492: "From the great heat which I suffer, the country must be rich in gold." Further, it will be recalled by those interested in the history of North America that a dispute (Nootka Sound controversy) arose between Spain and Great Britain over the sovereignty of the lands bordering the northwest coast of America. Spain contended she possessed sovereignty by authority of the Papal Bull of Alexander VI in 1493, but Britain took the view that ri ghts of sovereignty could be obtained only through trade and the establishment of colonies. Spain meanwhile had established a settlement on Nootka Sound and in 1789 seized four British ships in the sound. This act nearly precipitated a war but was finally resolved in favor of the British viewpoint in a convention signed on October 28, 1790. It appears probable that among the factors that influenced the Spanish decision was the advice given the Spanish king, Charles IV that gold was unlikely to occur in the northern regions of America because it was thought that the element was generated only in those regions most influenced by the sun. The references to the very fine-grained high-purity gold associated with a heavy sulfurous bituminous earth in Biringuccio's text is unclear as to just what type of deposit is meant. I suspect that the fine gold found in certain secondarily enriched sulfide zones below the zone of oxidization is intended. If so, this reference is the first in the literature to the very finely divided, nearly pure gold often found with fine-grained supergene (often black) sulfides (pyrite, marcasite, chalcocite) in the secondarily enriched zones of gold deposits. Finally, Biringuccio ponders the origin, as many have since his time, of gold in alluvial sands. After some discourse he concludes that the gold is transported by streams from oxidized and disintegrated bedrock deposits, an opinion opposed to that of Calbus and Albertus Magnus, who considered a chemical accretion theory for the origin of alluvial gold more probable.   Agricola, while retaining his belief in the Aristotelian concept of the four elements, discarded the alchemical idea of the transmutation of elements in the earth and inveighed against the astral theory of the generation of metals and the fundamentalist views of the origin of all things instantaneously at Creation, according to Genesis. On the contrary he concluded from his observations of ground waters and springs that mineral veins were deposited by circulating underground waters. Stripped of extraneous verbiage, Agricola's theory is that surface waters percolate downward, become heated, dissolve mineral matter, rise again, and deposit their mineral matter in the "canales." He considered the source of the heat to be deep-seated layers of burning bitumen (essentially coal), a fantastic idea, but one believed by many during the Renaissance and even later. Agricola was, therefore, a meteoric water secretionist, and it is a tribute to his genius to note that modern isotopic research has shown that certain type s of epithermal gold deposits probably originated in the manner he suggested. Agricola speaks of gold in many contexts, about human avarice for the precious metal, about its ores, and about its metallurgy. In De re metallica he classifies vein gold ores as follows (Hoover and Hoover, 1912, p. 107): "Now we may classify gold ores. Next after native gold, we come to the rudis, of yellowish green, yellow, purple, black, or outside red and inside gold colour. These must be reckoned as the richest ores, because the gold exceeds the stone or earth in weight. Next come all gold ores of which each one hundred librae contains more than three unciae of gold; for although but a small proportion of gold is found in the earth or stone, yet it equals in value other metals of greater weight. All other gold ores are considered poor, because the earth or stone too far outweights the gold. A vein which contains a larger proportion of silver than of gold is rarely found to be a rich one. Earth, whether it be dry or wet, rarely abounds in gold; but in dry earth there is more often found a greater quantity of gold, especially if it has the appearance of having been melted in a furnace, and if it is not lacking in scales resembling mica. The solidified juices, azure, chrysocolla, orpiment, and realgar, also frequently conta in gold. Likewise native or rudiv gold is found sometimes in large, and sometimes in small quantities in quartz, schist, marble, and also in stone which easily melts in fire of the second degree, and which is sometimes so porous that it seems completely decomposed. Lastly, gold is found in pyrites, though rarely in large quantities." In footnotes, rudis is translated by the Hoovers as crude, and they state that what is really meant is perhaps ores very rich in gold. In a further commentary they suggest that Agricola apparently believed that there were various gold minerals manifest by different colours, such as green, yellow, purple, and black. One wonders if Agricola was not here referring to the various tints that native gold may have in certain deposits. For instance I have seen yellowish gold, greenish gold, reddish gold, and black gold in veins and particularly in the oxidized zones of gold deposits. The librae is a measure of weight equal to 12 uncia, and the uncia is equal to 412.2 troy grains. The Hoovers give the value of the gold ore mentioned by Agricola as 72 oz 18 pennyweights per short ton. The earth having an appearance of being melted in a furnace is obviously scoriaceous limonite (goethite), and the mineral in scales resembling mica is probably jarosite. Both minerals are common in the gossans of surface enriched auriferous deposits, especially those with abundant pyrite and other sulfides. In De ortu et causes subterraneomm Agricola disagrees with the chemical accretion theory of Albertus Magnus for placer gold, maintaining that the gold is torn away from its parent veins and stringers and collects mechanically in the streams and rivers.  In the section on gold ores Ercker discusses the occurrence of the precious metal in some detail. From the translation by Sisco and Smith (1951 p. 93) we learn: "Beautiful native gold occurs most frequently in a white quartz; somewhat less often in a blue or yellow hornstone and also in blue, ferruginous, and yellow schists, but only very fine and in flakes. At the gold mine at Knin, located two leagues from Eule (Jilove) in Bohemia in the direction toward the setting sun, there occurs a greyish, argentiferous pyrites in a hard quartz, which, after crushing and washing, yields a beautiful high-grade native gold which is first not visible in the pyrites. At present I know of no place where more valuable gold is extracted or recovered directly from the ore. In addition, there is good native gold in all the auriferous placer ores, which are usually sandy but which are otherwise not all alike: in some, the gold occurs massive and in grains; in others, as flakes and light particles. The washing of almost all this placer ore also yields a heavy schorl or wolfram and in some cases grains of tin and ironstone. These have traveled much and far; together with the gold, they were torn from veins by the Flood, swept away, and collected together in such a marvellous and characteristic way that the colour and distinctive appearance of placer deposits can be clearly and easily recognized. This is how rivers and streams flowing over such deposits became inseminated with gold, so that at many localities, not only in far-away kingdoms and countries but also here in Germany, native gold is now washed from them and extracted. However, most of these occurrences are poor and will not repay the expense of washing. I cannot agree with those among the old writers who claim that it was the River Nile, which flows into the sea in Egypt, that inseminated and flooded the streams and rivers with native gold at the time of the Deluge, when all the sands became mixed up. Because, even if the aforesaid river is very large and does flow through vast Ethiopia (also called India), where much gold is reputedly found, and is supposed to be the mightiest of all the rivers, flowing the farthest, I still think that it is much too small to have been so rich in alluvial gold that it could have scattered gold into the sands and streams of so many places throughout the world. Then you hear a lot of talk here in Germany about various kinds of pebbles that are found in many parts of the country, in mountains and streams, and are carried away by foreigners and wayfarers. Many resemble gravel; some are brown, yellowish, or black and look like glass on the inside; usually they are round or square. It is said that gold is made from them. Personally I do not believe it because I have assayed these pebbles in various ways, in the fire and otherwise, but have never been able to find any gold in them. I learned this much, however, from trustworthy people, who heard the whole story from these wayfarers, that the pebbles do not contain gold, nor is gold made from them; but they are carried by the wayfarers for pay to Italy and other places where they are used as an addition in making beautiful pigments and enamels. Such pigments and enamels are there esteemed as highly and sold as dear as if they were gold. All of which is reasonable and credible, especially since there are other minerals he re in Germany that yield enamels and pigments. Furthermore, besides native gold, there sometimes occurs in the quartz of the gold mines at Eule in the kingdom of Bohemia a fine, grey, scaly ore, which on account of its colour is called ironman (hematite). This is rich in gold, which, however, contains silver, so that it cannot be compared with the other native gold occurring in quartz. There are many gold pyrites that contain not only gold but also silver, and usually more silver than gold; and pyrites that are very rich in copper and also contain silver, which silver is rich in gold; and white pyrites that contains no copper and very little silver and is yet auriferous. The copper-bearing pyrites whose silver contains gold are usually interspersed with fine quartz. Concerning the marcasite, of which many make fables and have written that it is a pyrites so rich in gold that it loses less than one-fourth in the fire and becomes more beautiful the longer it is roasted and kept red-hot, I have searched for it often and persistently but have never obtained it; neither have I ever encountered anybody who has seen such pyrites. As far as I can figure it out, this marcasite can and must be nothing but a very good, rich gold ore; whether it is given this name or another makes no difference."  To summarize, we can say that the Renaissance was the period when more modern theories on the origin of auriferous veins were considered, and when the origin of placer (alluvial) gold was debated. The Renaissance writers could not quite rid themselves of the Aristotelian and alchemical concepts of matter, but with Agricola a definite trend developed toward acute observation and the formulation of theories more in agreement with the facts presented by auriferous vein deposits. References and selected bibliography From: http://www.minelinks.com/alluvial/goldRenessance.html Rafal Swiecki, geological engineer. February, 2006 Terug naar Top van de pagina Terug naar Goud historie Terug naar de geschiedenis van het goud in de Klassieke periode Verder naar de geschiedenis van het goud in de Post-Renaissance periode
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