GOLD

Gold During the Renaissance

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 contain 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 (geothite), 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.

Lazarus Ercker (1530-1594), onetime assayer at Dresden, and later resident of Annaberg where he was chief superintendent of mines and comptroller of the Holy Roman Empire and Kingdom of Bohemia, published the treatise Beschriebung Allerfiirnemisten Mineralischen Ertzt und Berckwercksarten (Description of ore processing and mining methods) in 1574. This treatise is a systematic review of the analytical and assay methods then in use, some of which are still employed today in gold assaying; in addition the work contains long sections on the occurrence of the ores of gold, silver, copper, and other metals. Many translations of this famous treatise have appeared, the first in English in 1683 by Sir John Pettus while incarcerated in the Fleet prison in London and entitled Fleta minor or The Laws of Art and Nature."

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 here 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."

Ercker's mention of the Flood (The Deluge) as producing all of the gold placers in Europe and elsewhere is of interest because it is the first reference to this particular origin for placers that I can find. Of course the Flood was later to play an important role in the arguments about the origin of many types of mineral deposits, as we shall see later. The various kinds of pebbles mentioned by Ercker were probably tektites (moldavites), according to my observations in the old placer areas of Bohemia. The auriferous white pyrites is arsenopyrite.

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

Bandy, M. C., and J. A. Bandy. trans., 1955. De natura fossilium, by Georgius Agricola, (1546). Geol. Soc. America Spec. Paper 63, 240p.
Hoover, H. C., and L. H. Hoover, trans., 1912. De re metallica, by G. Agricola, (1556), Mining Mag. London. 637p.
Sisco. A. G., and C. S. Smith, trans., 1949. Bergwerk-und-Probierblichlein, Am. Inst. Min. Metall. Eng., New York, 196p.
Sisco, A. G., and C. S. Smith, trans., 195 1. Beschriebung allerfiirnemisten mineralischen Ertzt undberckwercksarten, u.s. w. (Lazarus Ercker's treatise on ores and assaying), Univ. Chicago Press, Chicago, 360p.
Smith, C. S., and M. T Gnudi, trans., 1959. De la Pirotechnia, by Vannoccio Biringuccio, M. I. 's. Press, Cambridge, Mass., 477p.