Thursday, May 15, 2014

The turquoise teeth of Languedoc

Although paleontology, as a defined science, has only been around for two hundred years, digging up fossils and trying to make sense of them far predates recorded history. In the 1880s, French archaeologists discovered a much-handled, trilobite fossil that had been drilled as if to be worn as a pendant. The occupation level in the cave where it was found has been dated to be fifteen thousand years old. For the bones of large extinct mammals, a small number explanations and uses have existed during the era of written history. The bones have been seen as the remains of human giants, monsters, unknown animals, and as mineral productions that merely resemble real bones. They have been used to inspire the faithful, as medicine, and, in Europe, as a source of turquoise.

On November 25, 1715, thermometer pioneer and all around smart guy, René Antoine Ferchault de Réaumur presented a paper at a public meeting of the French Academy regarding turquoise mines in Languedoc, the southwestern part of the kingdom. The mines, he said in passing, had been idle for twenty years due to wars and other disruptions. Before the paper was published, it was brought to the attention of Philippe II, Duke of Orleans, and newly installed regent for the five year old king, Louis XV. As regent, Philippe had the responsibility of finding resources to pay for those recent wars. Réaumur noted in the published version of his paper that, in the year since he had presented the paper, the Regent sent one of the members of his cabinet, Gilbert Charles le Gendre, to investigate. The governor of Languedoc was ordered to give his full cooperation and see if the mines could be brought back into production.

The aqua colored stone called turquoise was known and used in Europe in the same way as other precious stones. Most great collections included jewelry and religious items decorated with polished pieces of turquoise. Though the stone was well known, there was a great deal of confusion about its nature. The word "turquoise" was a fairly recent coinage meaning, essentially, "the Turkish stone." Turquoise originated somewhere in the East and was imported into the West by Turkish merchants. The problem with the name was that the Turks had not been between Europe and the Far East for that long. The Turks came from Central Asia. For centuries, Turkish tribes had been relocated by the Persian kings to their western frontier to serve various geopolitical purposes that are interesting, but not relevant here. By the early Second Millennium, they had become numerous enough and had Turkicised enough of the neighboring population that they began to form states independent of the Persian Empire. The identification of turquoise with the Turks probably dates to the Fourteenth Century when the Persians began to exploit new mines near Nishapur creating a dependable supply for export.

None of the writers of Réaumur’s time thought that turquoise was a new substance. The natural historians of Antiquity, such a Pliny and Theophrastus, described several blue and blue-green stones whose modern identity was uncertain. For the later naturalists, the relevant question was which, if any, of those stones referred to turquoise? Réaumur identified two possible contenders in Pliny’s Natural History: one called borea and the other calais. The belief of his peers was that, during the thousand years between the fall of Rome and the arrival of Nishapur turquoise, whatever word the ancients had used for the stone had fallen into disuse and been forgotten. When Turkish merchants began offering it as a new commodity, European merchants, lacking another name, called it the Turkish stone. The etymology suffered some problems, such as: why didn't anyone ask the Turks what it was called. Additionally confusing was the fact that the earliest known use of the word "turquoise" slightly preceded the arrival of the Nishapur stones in Europe and had been used to describe a different stone—a yellow-white one—being imported from the East by Turkish merchants.

The uncertain historical identity was followed by a second problem, which was particularly important to Réaumur. He wanted to know whether Persian turquoise and Languedoc turquoise were the same substance. This turned out to be a very complicated problem. The ancient writers being of no help, he combed through more recent writers to find an answer, but found them just as confused as he was. The writers he cites in his paper describe two types of turquoise: Oriental, meaning Persian, which was regarded as being the best quality, and Occidental, found in parts of Europe, and which was regarded as being of lower quality. The French traveler and gem merchant Jean-Baptiste Tavernier, who is best known today for having brought the great blue gem we call the Hope Diamond to Europe, spent considerable time in Persia and knew something of the mines around Nishapur, though he did not personally visit them. He wrote that there were two different mining districts and that each produced a different type of stone. The harder, bluer stone was called "old rock" and the softer, paler stone was called "new rock." Finally, there were reports of blue stones occasionally turning up in the New World. Oriental hard rock, Oriental soft rock, European, and American stones were at one time or another all called turquoise, but were they all the same stone?

The lecture Réaumur presented to the Academy was significantly different from the paper published in their journal almost two years later. The published paper contained additional information Though a copy of the lecture has not survived, Réaumur was fairly clear about which details were c he learned after the lecture thanks to Gendre's investigations as an agent of Philippe II. Réaumur says that he never was able to visit the mines in person; his original presentation must have been entirely based on written sources. None of these sources had a lot to say about Languedoc turquoise, but they all mentioned one curious detail that did not appear in other descriptions of the stone. Languedoc turquoise did not come out of the ground showing the bright blue color that made the stone so desirable. To achieve that color, it had to be treated with fire. Gendre provided Réaumur with samples from the mines to experiment on. The samples surprised him. Several of them looked like very large teeth.

Two of the teeth Réaumur examined. He handled at least six complete teeth and several fragments. Source.

Along with his purely scientific interest, Réaumur had a very practical reason for looking into the mines. For five years he had headed a committee charged with cataloging the useful arts and manufactures of the kingdom. Even after his work on the committee was completed, for the rest of his life he maintained an acute interest in the practical application of the sciences for the good of the realm publishing papers on beekeeping, silk production, and iron smelting. It’s likely that the first draft of his paper was an official report and that this was how the mines came to the attention of Philippe and Gendre.

A significant part of Réaumur’s paper was dedicated to the mines themselves and the method of converting the stones into turquoise. The earliest mention he could find for the mines was from 1628 and the locals said that they had been idle for about twenty years, though they were starting to come back into production. Most of the mines were near the town of Simore in the Gers district of Lower Languedoc. The turquoise was found in a layer of bluish sand several layers below the surface. The mines had to be heavily timbered because of the sandy soil. Some mines were as deep and fifty feet deep and he believed that there was plenty of turquoise still to be found. When discovered in the ground, the turquoise pieces were light yellow, tan, or light blue. To become turquoise, the pieces needed to be baked in special ovens that were a little larger than a coffin. Once the fire created a good bed of coals, the pieces were placed in a small cup, which he called a shoe (sabot), and placed on a ledge in the oven. The stones and the oven required constant attention. Wood had to be added to keep the temperature high and the unripe turquoise needed to be regularly monitored for color. The time needed to reach the best color ranged from less than four hours to over twenty four. If left in the oven for too long, the pieces would first turn green and then black, neither of which had any commercial value.

The ovens and tools for preparing the turquoise. Source.

In going over literature that specifically mentioned Languedoc turquoise, Réaumur saw that, of the five sources he discovered (I haven’t found any more), three mentioned the necessity of fire in bringing out the color and two mentioned fact that the turquoise ore looked like bones. His contemporary informants told him that the locals even referred to pieces as arms, legs, and teeth. He examined the pieces that had been sent to him with very carefully with a microscope and saw minute structures that convinced him that the ore really was the petrified remains of bones and teeth and not just rocks that looked like them. There was enough variation among the teeth that he suspected they were the remains of more than one species of animal. For a man of science, he showed very little curiosity about what those species might have been. In two sentences he says they are probably the remains of kind of sea animal since nothing similar lives on the land and leaves it at that.

There was a good hint to the identity of one of the animals in the earliest description of the Languedoc turquoise. In 1728, Guy de la Brosse wrote in his On the Nature, Virtue, and Utility of Plants: “There is a stone that has figure of a horn, the consistency of stone, and, exposed to graduated heat, gives true Turquoise: it is called unicorn mineral (Licorne minerale), because it looks like the horn of an animal. It is effective against all kinds of poisons.” The unicorn mineral, also known as unicornu fossile and ebur fossile, was the name given to fossil ivory, which almost always meant tusks of mammoths or of a few other species of prehistoric elephant. Since antiquity, unicorn horns had been believed to be an antidote for all poisons and even to have the power to detect poisons nearby. During the poison panic of the Renaissance, narwhal teeth were worth considerably more than their weight in gold. There was some question about whether fossil ivory came from unicorns or some other animal, but there was little doubt that it had the same anti-poison properties. In de la Brosse’s time the belief that the only security against the poisoners that lurked behind every tapestry was a large piece of unicorn horn had begun to fade. The price had been dropping since the last years of the previous century though the belief that powdered unicorn horn was good medicine hung on in some circles right up to Réaumur’s time. His lack of interest in the animal that produced the Simore teeth is curious because, when he made his investigations, it was generally accepted that most fossil ivory came from elephants and not sea creatures. Testing modern ivory to see if it too could be converted into turquoise would have been an obvious line of research for him to pursue.

Having blown off the question of whose teeth the Languedoc turquoise came from, Réaumur was left with one final question: was this the same substance as Persian ivory; were the Persians also baking bones and teeth to get turquoise? Réaumur took a selection of stones to a Paris jeweler who was familiar with Persian turquoise. The jeweler told him that some of the stones were old rock and some of them were new rock. If Tavernier was to be believed, this shouldn't have been possible. The two should not be found together in the same place. The jeweler held firm in his identification. Réaumur's microscopic examinations revealed that Persian turquoise did not show any of the organic structures that he saw in his samples from Simore. He was confident that his turquoise was a different substance than Persian turquoise. He expressed no opinion on the question of whether or not old rock and new rock Persian turquoise were the same substance.

Réaumur's paper was influential, but not the last word on the topic. In Bordeaux, local officials experimented with baking newer bones in the hope of producing their own turquoise. The experiment was a failure. For the next century, various writers argued about whether or not the Languedoc stones were “real” turquoise. Interest in the stones finally waned in the early Nineteenth Century when Gotthelf Fischer from Moscow University made a study of various turquioses and named the French turquoise odontolite. Now that it had a name, the stone went out of fashion. The main academic interest in it was nailing down exactly which chemicals, assumed to be metals, gave odontolite its color. It was a frustratingly elusive problem only solved in the Twenty-first Century.

Réaumur donated four of the teeth to the royal collections. They are the same ones he used as illustrations for his paper. He must have kept those. When Louis-Jean-Marie Daubenton organized and cataloged the collections in the 1750s and ‘60s, he placed the teeth with hippopotamus bones. It was an inspired error. He also cataloged mastodon teeth from North America as belonging to hippos. He believed that both sets of teeth came from a giant, unknown species of hippo. The two were related to each other, but not to hippos. In 1796, Georges Cuvier, a rising young star in the French scientific scene, confidently announced to the world that mammoths and mastodons were not elephants, they were two extinct species only related to elephants. Extinction was a controversial idea at the time. Cuvier became an unofficial keeper of the list for extinct animals. In 1806, after examining Réaumur’s turquoise teeth in what was now the national museum, he added a new species to the list. He called it Mastodon angustidens. Over the years, the species has been bounced from genus to genus; today it’s called Gomphotherium angustidens. Three of the teeth in the museum came from this species and it is by far the most common proboscidean fossil in Languedoc.

Reconstruction of G. angustidens by Charles R. Knight. Notice the long jaw and four tusks. Source.

Though the Simore mines no longer produce turquoise, the digging hasn't stopped there. With the science of paleontology taking off, French scientists traveled to the region to hunt for ancient bones. During the Nineteenth Century, Edouard Lartet worked in the region and found bones from ninety-eight different genera of mammals, some extinct and some still living. Others followed. Lower Languedoc, it turns out, is a treasure chest of Miocene fossils. The Miocene ran from 23 to 5.3 million years ago. G. angustidens lived during the latter half of that. Many other species have been discovered in the region including other proboscideans. Fossil bones are plentiful enough there that, sooner or later, paleontologists would have begun to dig there even without Réaumur's guidance. As it was, it was sooner, and all because he became curious about reports of turquoise around the town of Simore and asked questions.

1 comment:

Gav said...

Yay for Réaumur! Yay for the accent aigu! Bring back the Réaumur temperature scale!

How on earth do you find this fascinating stuff? You know, you really ought to write a book on it and get it published, maybe, please?