GOLD

Gold During the Renaissance

For more information on a likely place for the generation of this kind of gold you should know that gold schlich can probably be coaxed out of spots where many little weathered furrows (i.e. riffles) are found under the soil where the placer gold occurs. These resemble the little veins or cracks that are sometimes found to run through the loam in loam pits. And where the little furrows bunch or multiply, they multiply and increase the mineral Power from the earth so that more gold is generated.

Gold that is generated in a pyritic deposit is mixed with many and varied worthless impurities because pyrites is made from contaminated sulfur and an impure earthy matter. But through the influence of the Sun and Heaven, and given enough time, the finest part of the pyrites is gradually cleansed and boiled into a persistent gold ore, which must be separated from the impure pyrites by the industrious application of strong fire.

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 attached 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.

Similarly, where the yellow clay occurs as a vein, it is promising to mine, provided the vein has a fine country rock in its hanging and foot-walls. Furthermore, where native gold is found in stringers that run near a vein, it should be observed where the stringers join the vein; and there you may confidently start to mine and sink a shaft. If, however, such stringers swerve away from the vein, you are likely to be disappointed unless they join another vein. Wherever hanging gold is generated in various kinds of rocks in the most rugged mountains that are completely barren of soil, trees, and grasses. And of all the rocks for such metal the best is a blue stone called lapis lazuli, which has a blue colour similar to the sapphire, but is neither so transparent nor so hard. It is also found in orpiment and even more it is found associated with the ores of other metals. Much is also found in the river sands of many regions. That which is found in mountains is in the form of veins between one stratum and another, united with the blue rock, and indeed is much mixed in with this. They say that such ore is better the heavier and the more full of colour it is, and the more flecks of gold appear in it. They also say that it is generated in another rock similar to saline marble but of a duller colour, and in still another rock whose colour is yellow with many red specks in it. They also say that it is found in certain black rocks, scattered loosely about like small stones in a river. And furthermore they say that it is likewise found in a certain bituminous earth of colour similar to clay and that such earth is very heavy and has a strong sulfurous odour.

The gold extracted there from is very beautiful and almost completely pure, but it is very difficult to get out because it is of the finest grain, almost like atoms, so that the eye distinguishes it with the greatest difficulty. Nor can one proceed as with lapis lazuli or other rocks or as one treats river sands, for when it is found there, and even more when it is washed, it falls only with difficulty to the bottom, and, growing vitreous on melting, it becomes pasty with the matrix and its earthy matter. Nevertheless, in the end it is possible to recover it using the greatest patience with one method or another and finally with mercury.

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 these 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, copper, 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.

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Rafal Swiecki, geological engineer email contact

This document is in the public domain.
March, 2011