GOLD

Gold During the Classical Period

"The mountain torrents are said to bring down gold, and these barbarians (Soanes) catch it in troughs (sluices) perforated with holes and in fleecy skins." Strabo's reference is probably to the river Phasis (the present Rioni in Georgia, draining from the Caucasus), which drained the Colchis region, supposedly one of the goals of the Argonauts in the legend of Jason. Describing the gold deposits of Egypt and Nubia Strabo quotes Agatharchides of Cnidus (c. 132 B.C.) freely and gives us an insight into the geological setting of some of the deposits. In an interpretative translation we learn: "There (in Egypt and Nubia) the rock is black and full of streaks and veins of a mineral with a remarkable whiteness the lustre of which surpasses the most brilliant natural materials."

Obviously, Strabo, like Diodorus Siculus, is speaking of gold-quartz stockworks in greenstones (amphibolites) or in black slates or schists. The white mineral is probably milky quartz. These interpretations are supported by recent work in Sudan (Fletcher, 1985; Gaskell, 1985).

A number of Roman writers have left works of interest to geologists and mineralogists. Lucretius (99-55 B.C.) author of De rerum natura, a famous philosophical work, describes many natural phenomena but mentions gold and mineral deposits in only a cursory manner. Vitruvius (c. 27 B.C.), the renowned Roman military engineer and architect, likewise treats the subject of mineral deposits and gold only briefly in his De architecture. Pliny the Elder (A.D. 23-79) was the only Roman to engage in extensive natural history studies; of all the classical writers he alone has given us a documentation of the works of earlier ledge of minerals and mineral deposits writers and a summary of the know extant at the beginning of our era. His extensive travels, as a onetime cavalry officer and later prefect (admiral) of the Roman Fleet under Vespasian, are recorded in thirty-seven books in his encyclopaedic Historia naturalis. This famous treatise was suddenly terminated by Pliny's death as a martyr to science when he was suffocated by volcanic gases as he sought to study the cause of the violent eruption of Vesuvius in A.D. 79.

The Historia naturalis is a great assemblage of fact, fancy, and fiction written from both observation and hearsay. Where observation prevails, the narrative is precise and logical; where hearsay predominates much of the text is fanciful and sometimes bizarre. Book 33 treats of the natural history of metals, and in it the first section is reserved for gold.

After a long discourse on the avarice of man for gold, the wearing of gold rings and other golden adornments, coinage, other uses of gold, and the special qualities of gold, Pliny turns to methods of discovering and mining gold ores. In the translation of Rackman (1968, p. 53) with my explanations in parentheses we read:

"Gold in our part of the world-not to speak of the Indian gold obtained from ants or the gold dug up by griffins in Scythia is obtained in three ways: in the detritus of rivers, for instance in the Tagus in Spain, the Po in Italy, the Maritza (Hebrus) in Thrace, the Sarabat (Pactolus) in Asia Minor and the Ganges in India; and there is no gold that is in a more perfect state, as it is thoroughly polished by the mere friction of the current. Another method is by sinking shafts; or it is sought for in the fallen debris of mountains. Each of these methods must be described. People seeking for gold begin by getting up (searching for) segullum -that is the name for earth that indicates the presence of gold. (Beneath) this is a pocket of sand, which is washed, and from the sediment left an estimate of the vein is made. Sometimes by a rare piece of luck a pocket is found immediately, on the surface of the earth, as occurred recently in Dalmatia when Nero was emperor, one yielding fifty pounds weight of gold a day. Gold found in this way in the surface crust is called talutium if there is also auriferous earth underneath. The otherwise dry, barren mountains of the Spanish provinces, which produce nothing else whatever is forced into fertility in regard to this commodity.

Gold dug up from shafts is called 'channelled' or 'trenched' gold; it is found sticking to the grit (gangue) of marble, not in the way in which it gleams in the lapis lazuli of the East and the stone of Thebes and in other precious stones, but sparkling in the folds of the marble. These channels of veins wander to and fro along the sides of the shafts. . . . The third method will have outdone the achievements of the Giants. By means of galleries driven for long distances the mountains are mined by the light of lamps."

In a following passage, Pliny deals with the constitution of gold. In the translation by Rackman (1968, p. 53) we read:
"All gold contains silver in various proportions, a tenth part in some cases, an eighth in others. In one mine only, that of Callaecia called the Albucrara mine, the proportion of silver found is one thirty-sixth, and consequently this one is more valuable than all the others. Wherever the proportion of silver is one-fifth, the ore is called electrum; grains of this are found in 'channelled' gold."

The reference to the Indian gold ants and the Scythian griffins comes from Herodotus and is a tale spun through the ages down to the present day, being repeated and analyzed by Strabo and Pliny and by T. A. Rickard as late as 1930. Adams (1938) discusses the probable origin of the tale in detail. My personal opinion is that in ancient times someone found eluvial gold particles in ant (termite) mounds somewhere in Asia, from whence sprung the fable of the gold-digging ants. In this respect, it was well known by the old prospectors that ants would collect splendid particles of metals and minerals such as gold and galena. Some birds have a similar penchant. The griffin tale from Scythia may be similarly based on the circumstance that the spoil near certain animal burrows (e.g., marmot) in auriferous regions may contain particles of gold.

The material called segullum (or segutilum in some Latin versions) should probably be translated as gossan. Segullo is still used by Castilian (Spanish) prospectors to define the gossanous material capping certain auriferous deposits. I can find no translation for the Latin word talutium (or talutatium in some versions); I suspect that nuggety or eluvial was meant. The use of marble for the gangue of gold veins is evidently an error; quartz was obviously meant. Channelled gold in the second excerpt should be translated as vein gold.

In a later passage, Pliny deals with the oxidation processes of copper minerals in gold veins. In the translation given by Bailey (1929, pt. 1, p. 105) it is stated:
"Chrysocolla is an exudation found in the shafts, which we have already mentioned. It oozes down the vein of gold, and its muddy substance is congealed under the influence of the winter cold until it is as hard as pumice. It is well established that the best quality forms in copper mines and the next best in silver mines. It occurs in lead mines also, but this kind is inferior to that found in gold mines. In all these mines, however, it is also prepared artificially (though its worth is far below that of the natural product) by leading a gentle stream of water into the vein all through the winter until the month of June, and evaporating the extract in June and July. It is therefore perfectly clear that chrysocolla is none other than a decomposition product of a vein of metal."

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Gold in: Primitive Classic Medieval Renaissance post-Renaissance period.

Gold: Deposits Transport

Rafal Swiecki, geological engineer email contact
February, 2008

This document is in the public domain.