Nederlandse Goudpan Vereniging

"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 Renaissance, rebirth, or more strictly speaking the intellectual
revival of Europe in the fifteenth and sixteenth centuries, was marked
by the advent of Humanism, a revolution in art, sculpture, and letters
but with relatively little progress in natural science, and during much
of the sixteenth century by the Reformation led by the son of a miner,
Martin Luther (1483-1546). The Humanists devoted themselves to the study
of the language, literature, and antiquities of ancient Greece and
Rome, hoping to find in the past a novel form of thought about nature
for the future. They considered themselves in rebellion against the
scholasticism of medieval times and were preoccupied with man in
relation to human society rather than to God.





The foundation of the Vatican Library at Rome by Pope Nicholas V was a
landmark of the Renaissance, as were also the writings of Alberti,
Castiglione, Machiavelli, Erasmus, More, Shakespeare, and Luther in the
fields of social and political thought, literature, and religious
doctrine. In music, architecture, sculpture, and art it was the period
of Orlando di Lasso, Palestrina, Brunelleschi, Raphael, Donatello,
Botticelli, Titian, Cellini, Leonardo da Vinci, Durer, Holbein, van
Eyck, Breughel, and Michelangelo. As one gazes up at Michelangelo's
Creation of Man on the ceiling of the vault of the Sistine Chapel of St.
Peter's in Rome, one sees in Adam a veritable symbol of awakening
Renaissance man marvelling at all about him.





Capitalism, the monetary system whereby talent and ability, not origin
and estate, are the qualifying factors for its aristocracy, appeared in
its first manifestations during the early Crusades (eleventh and twelfth
centuries), grew slowly during later medieval times, and expanded
rapidly during the Renaissance with the establishment of banks in Genoa,
Florence, Augsberg, Lyon, and Antwerp, all controlled by powerful
families. Among these were the Fuggers, initially weavers in Augsburg,
of whom one, Jakob Fugger the Rich (1459-1525), banker to the Hapsburgs
and the popes, created a financial empire through extensive investment
in mining in Austria, Hungary, and Spain, thereby monopolizing the
silver, lead, copper, and quicksilver production of Europe. This
expansion of capitalism and investment in mining in central Europe, the
Tyrol, and Spain stimulated mining and metallurgical technology and the
publication of various tracts dealing with these subjects, some of which
are described next.





The Humanists contributed little to the progress of natural science
because they were on the whole more interested in the relationship of
man to man than in that of man to nature and more absorbed in literature
than in chemistry, physics, and mathematics. Nevertheless, as
scientists we owe them a debt of gratitude for accurate translations of
many Greek and Roman scientific treatises that were to form the bases
for the advance of science in modern times. These treatises were to have
a great influence on Leonardo da Vinci, Copernicus, and Galileo. We
also find this influence reaching out to Calbus, Biringuccio, Agricola,
and Ercker, the most celebrated of the earth scientists and
metallurgists of the Renaissance.



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





The invention of printing in the mid-fifteenth century was followed
during the Renaissance by many small treatises on various technical
arts, among which those dealing with mining and metallurgy are of great
interest to us in the context of gold. Here belong
Bergwerk-und-Probierbziehlein by Calbus of Freiberg, De la Pirotechnia
by Biringuccio of Siena, De re metallica by Agricola of Joachimsthal and
Chemnitz, and Beschriebung Allerfiirnemisten Mineralischen Ertzt und
Berckwercksarten by Ercker of Annaberg. All of these works became
standard references immediately on their publication and remained so for
more than a century.



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:





"It should be realized that for ores to grow or to be born requires an
agent to exert an influence, and a passive thing or matter that is
qualified to be influenced. In the words of the naturalists, the common
maker of ore and all other things that are born is Heaven with its
movement, radiance, and influence. The influence of Heaven is
diversified by the movement of the firmament and the countermovement of
the seven planets. In this way each metallic ore receives an influence
from its own particular planet, specifically assigned to it because of
the characteristics of the planet and the ore, and also because of their
conformity in warmth or frigidity, moisture or dryness. Thus, gold is
made by the Sun or his influence, silver by the Moon, tin by Jupiter,
copper by Venus, iron by Mars, lead by Saturn, and quicksilver by
Mercury. That is why Hermes and other learned men often call the metals
by these names, that is, they call gold sun, in Latin sol, and silver
moon, in Latin luna....




But the passive thing, or the common matter of all metals, is,
according to the opinion of the philosophers, sulfur and quicksilver,
which, through the movement and influence of Heaven, must be joined and
hardened into a metallic body or an ore. Some think that through the
movement and influence of Heaven vapours or fumes (called exhalationes
minerales) of sulfur and quicksilver are pulled up from the depth of the
earth, which, when ascending through fissures and fractures [which
become the veins and stringers] are united by the influence of the
planets and are made into ores.
But there are others who do not believe that metals are made from
quicksilver because metallic ores occur in many locations where no
quicksilver is found.
They assume, instead of quicksilver, a moist, cold, muddy matter,
without any sulfur, that exudes from the earth as if it were its sweat,
and think that all metals are made by its commingling with sulfur. But
never mind; if you understand and interpret them correctly, both
theories are right; that is, ore or metal is made of the moisture of the
earth, called matter of the first order, and of vapours and fumes,
called matter of the second order, both of which shall here be called
quicksilver. Thus, in the mingling or union of quicksilver and sulfur in
ore, sulfur acts as the male seed and quicksilver as the female seed in
the birth or conception of a child. That is the story of sulfur as a
special, qualified maker of ores or metals."



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.






The better to recognize such locations and streams that carry gold, it
should be remembered that in general gold is likely to be born in
streams in which precious stones are found, such as amethysts, rubies,
rock crystals, and other highly refined pebbles, which are an indication
of the fitness of the place. According to the opinion of Albertus
Magnus, hot and dry fumes or exhalations are seldom extracted from the

earth without being accompanied by warm, moist vapours. The gemstones
are wrought and born of dry fumes; and the clearer, finer, and nobler
the fumes are, the more beautiful and the better and harder will be the
gems. Metals are wrought and made from moist vapours, and how strong and
good the metal is will depend on how clear, pure, and well-digested the
matter is from which the vapours or mists are extracted. Since moist
and dry exhalations rise together, but each is hardened according to its
own nature, it is a very reliable indication of the occurrence of gold,
as said before, if precious stones are found in a river. Also, where
you find in a river or nearby little crystals of tourmaline of a dense,
fine structure a gold occurrence is not far off. It is, however,
essential that the crystals be very fine because where the coarse kind
is found, there is little hope for an occurrence of the best and finest
of the metals, the gold. The value and actual gold content of the gold
that is generated under the overburden near swamps depends on how much
of the grey or black imagnetitel sand that together with the little
leaves or grains of gold constitutes the schlich is mixed up with it in
smelting. In many places this schlich contains more silver than gold,
and sometimes even copper, so that the gold is less valuable wall
stringers that contain native gold leave a vein either sideward or
downward, it is advisable to explore for other veins; by such foresight
the stringers and the veins may be worked together."



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.





Vannoccio Biringuccio (1480-1539), metallurgist, master founder, and
munitions advisor to the Petruccis of Siena and to Pope Paul III in Rome
wrote the Pirotechnia, probably in 1538, and it was published in 1540,
the year following his death. The work consists of ten books, most of
which are concerned with metallurgy, pottery, and munitions. In the
preface to the first book a guide to prospecting, developing, and mining
mineral deposits is outlined, and in the first chapter, entitled,
"Concerning the Ore of Gold and its Qualities in Detail", we read from
the abbreviated translation of Smith and Gnudi (1959, p. 28) the
following:



"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.






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 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.





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
footwalls. 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 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."





We see from these passages that Biringuccio, while clinging to the
astral (astrological) theory of the origin of gold, nevertheless gives
us a fairly accurate account of the natural occurrences of the precious
metal. In later passages (p. 41) he questions the veracity of the
alchemists and advises Messer Bernardino di Moncelesi of Salo, to whom
the first book is addressed, as follows:



"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.





Georgius Agricola (Georg Bauer or George the Farmer, 1494-1555), a name
familiar to all miners and earth scientists, was a native of Glauchau
in Saxony and later physician in Joachimsthal (Jachymov) and burgomaster
of Chemnitz (Karl-Marx-Stadt), two of the foremost mining towns in
Renaissance Europe. Agricola, as a classical scholar and humanist, made
many contributions to medicine, chemistry, mathematics, theology, and
history, but his most important works were in mineralogy, geology, and
mining. His views in earth sciences mark a transition from those of
medieval to those of modern times. Among his writings on mineral
deposits those of greatest interest in the context of gold include
Bermannus, Sive de re metallica dialogus (1530), a short work (dialogue)
on the mines and ores of the Erzgebirge; De ortu et causes
subterraneorum (1546), a work that deals among other subjects with the
origin of mineral deposits; De natura fossilium (1546), generally
credited as the first systematic textbook on mineralogy, th e system
employed being based on the physical properties (e.g., colour, lustre,
taste, etc.) of minerals; and De re metallica (1556) dealing with the
prospecting, developing, mining, and metallurgy of mineral bodies. Many
of the observations made in these works are Agricola's own although he
sometimes borrows from the Bergb chlein and other now nonexistent
treatises. The classic translation of De re metallica, with appended
notes on most of Agricola's other writings, is that by Herbert Clark
Hoover, geologist and mining engineer and onetime president of the
United States, and his wife, Lou Henry Hoover, scholar and classicist
(Hoover and Hoover, 1912).





Agricola clearly recognized the difference between rocks and minerals,
and in his work on ore genesis, De ortu et causes subterraneorum, he
recognized that many types of mineral deposits (veins) are concentrated
in openings (fissures) which he called canales. These he thought were
late events (i.e., later than the strata), caused by the solution
effects of circulating underground waters. Agricola recognized three
types of veins: normal steep-dipping veins, (vena profunda), composite
vein systems, impregnations, and stockworks, (vena cumulata), and bedded
veins (vena dilatata).



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.





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 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."





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

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