DETROIT () -- The world has had many gold rushes, two uranium rushes, so far that I can remember, and now, I think we're on the verge of a tellurium rush. What's that all about?
It's about the time lag between the discovery of a chemical element and the discovery of a use for it. Briefly, until the last quarter of the 18th century there was no glimmer of a modern theory of the chemical constitution of nature.
The "elements" as defined by the ancient Greeks, earth, air, fire and water were pretty much accepted as the fundamental constituents of the material world. Between the renaissance and the American Revolution, though, alchemists were evolving into chemists and metallurgists as it was discovered that earth and air could be broken down into many distinct metals and airs. This came about because the alchemists defined themselves by their single minded agenda: the "creation" of gold from "baser" substances.
This phrase is commonly misunderstood by Hollywood film makers to mean the creation of a valuable substance, gold, from less valuable substances, dirt, bat's wings, "common" metals, such as lead and so forth. Actually the alchemists were saying that gold was nature's perfect, immutable, end product of construction, and they believed that they could find the "constituents" of gold in other, more common, substances and build gold from them.
A great deal of work was done in furtherance of the above goal, and in the process, modern chemistry and metallurgy were born from the attempt to discover the building blocks of nature. The nineteenth century was, for chemistry, among other things, the great age of the discovery of the chemical elements.
Unlike all previous periods the investigations were not carried out because there was a preconceived "use" for the new elements, but as a great intellectual crusade to break nature down into understandable segments, such as chemistry, physics, metallurgy, biology, etc., and to find patterns in nature, i.e., physical laws, to understand how the world functioned.
The "elements" of the ancients were joined by oxygen just over 200 years ago. By 100 years later a pattern, the periodic table of the elements had been discovered that led chemists to realize that oxygen was in a family of elements that included sulphur, known from ancient times, and two newly discovered - in the nineteenth century - siblings called selenium and tellurium. At the very end of the nineteenth century the last of the great intuitive chemists, Marie Skladowska Curie, would add polonium, a radioactive element, to oxygen's family.
Investors now take note. The reason that some elements are so hard to find in nature is that they are by products, they are always found in conjunction of other, more common, elements. Frequently they are chemically combined with the more common element or metallurgically alloyed with them, or a combination of both.
To cut to the chase: Native gold comes in many colours, because of the presence of additional elements dissolved in (i.e., naturally alloyed) or actually chemically combined with it. Copper, for example, can give us rose shades of gold, platinum gives "whites," aluminium gives a beautiful purple colour, and, you probably already guessed, tellurium combined with gold gives it a black colour. This black material, found as an ore called calverite, is the second most common form of gold found in North America. Wikipedia has a nice compact article on tellurium, which contains more technical information on tellurium bearing minerals for those interested.
Prospectors in the nineteenth century probably glommed onto the gold in gold telluride, calverite, after noting that if they used the heavy black mineral they often found with native gold, to douse a fire or build a support for a fire that it would occasionally catch fire giving off an awful stench of garlic, but the cold embers might have a fleck or two of gold remaining after the tellurium had burned away as volatile tellurium oxide. The chemists were thrilled to have a source of tellurium and some, very few, miners had found a source of more gold, albeit at the cost of needing some complex chemical processing to get rid of the tellurium.
As most of RI readers already know, gold is today recovered in substantial quantities as a byproduct of copper refining, and visa versa. The gold that is dissolved in the copper, naturally, is released when copper is electro refined, and is collected in filter bags of anode 'slimes." Other common byproducts of copper separated by electro refining are silver, platinum, selenium and tellurium.
There is no primary tellurium mine in the United States or anywhere else. Tellurium and selenium are recovered mainly from copper ores mainly because they must be removed for the most common applications to be feasible. Their presence can cause the copper to be brittle. Some Mexican copper ore is less valuable for wire drawing than its American counterparts, because of its high selenium content. American domestic lead ores frequently also contain tellurium as a byproduct. Perhaps the best survey of tellurium sourcing and availability is that of the USGS.
Tellurium was almost universally left in the tailings until just after World War II; it had almost no commercial uses.
The discovery of solid-state electronics changed that forever. The first solid-state electronic devices depended on a property discovered in the very common element, silicon. When silicon was ultrapurifed and also prepared in a single crystalline form, i.e., the entire sample with which one was working was one crystal, it did not conduct electricity, but with the addition of a tiny amount of another element from a particular group it could be made to conduct electricity. The man made semiconductor had been born-in the U.S., of course-and the second industrial revolution was underway. That was 60 years ago.
A flood of investigations of the electronic properties of materials ensued between this first discovery of man made, designer, so to speak, semiconductors and the present day. It has been the modern equivalent of the nineteenth century's search for chemical elements, but with a key difference. Investigators are looking not only to expand knowledge but for specific properties, which can be commercialized.
Solid state electronics, based on crystalline silicon and germanium, originally discovered in a rare mineral and only produced at first as a tiny byproduct of coal (ash), soon did away with essentially all of vacuum tube electronics. Before that first revolutionary changeover was completed some researchers at Bell Telephone Laboratories (the place where the first transistor was made in 1947) had looked at and discovered semiconducting properties in non-silicate (i.e., non ordinary window) glasses. The disordered solids, described as glassy or "amorphous," made from, for example, germanium, arsenic and tellurium, could be formulated so that they could be used as electronic switches or memory devices as long as very small currents were involved. This was in the 1950s.
In the early 1960s an intuitive genius from Akron, Ohio, Stanford R. Ovshinsky, decided that amorphous semiconductors could be made that would switch and conduct large(r) currents and could be made much more cheaply than single crystal silicon or germanium devices. He also did extensive research on the use of amorphous materials as non-volatile computer memories. They caught the industry's attention early on, because hey could be made to "remember" their setting even with the power "off."
It has been 44 years since I made, in a cobbled together vacuum coater, at the inventor's Stan Ovshinsky's direction, a layered thin film of tellurium, arsenic, germanium, arsenic, and tellurium. After we figured out how to make non-destructive electrical contacts to the thin film I watched as Stan cranked up the voltage, by hand, until suddenly the oscilloscope showed that after a threshold voltage had been passed the film conducted electricity and then when the voltage was reduced the film stopped conducting electricity. I well remember the stench of burning tellurium in the air that day.
The crystalline semiconductor revolution continued in full swing for many years after that day, but slowly the properties of tellurium based glasses became useful. I remember also the very day that Stan said, looking at some crystalline dots we had created with a laser in an otherwise amorphous film under a microscope, "Isn't that what a recording does?" It was, and the recordable CD and DVD were both direct results of that discovery as their pioneering Japanese manufacturers will tell you.
But it is just now in 2007, nearly 40 years after the above observation, that Stan Ovshinsky's discovery of what others call phase change memory and what he calls the Ovonic effect may well explode in unpredictable ways and drive the demand for the very rare element tellurium through the roof.
Intel and Samsung both will, this fall, introduce flash memory replacements made from non-volatile amorphous technology that can be used, erased, and used again indefinitely, but, rather than being crystalline silicon technology based, are made from tellurium based glasses composed of germanium, antimony, and tellurium. These amorphous technology flash memory successors will replace some magnetic hard drive uses, but their (unpredictable) explosive growth could be in inexpensive, reliable, smart cell phones, kids' toys, improved RFID chips and as many other applications, some of them undoubtedly new, that electronic engineers can think up.
Here is an announcement by Intel and a brief retrospective of the technology's previous false starts in a recent, yesterday, in fact, trade journal's comment:
"Phase change memory consumes little power, lasts far longer than conventional memory, and can hold large amounts of data in a small space. The bits also can't flip or get corrupted easily. The real challenge has come in manufacturing and reliability. Switching a bit from crystalline to amorphous requires pulsing it with an electronic charge or heating it up rapidly to 600 degrees Celsius without flipping the neighboring bits."
Read the whole article. It is mostly non technical, and very illuminating about a technology now coming into its own, finally.
A uniquely tellurium-based vehicle for investors is not yet here. Look for copper producers to now "discover" that they are tellurium producers. This will be funny, because many copper producers until just a very few years ago didn't even care about molybdenum.
Perhaps a hedge fund will buy up all the physical tellurium it can find and create an immediate run up in the price. Note that this could put a damper on tellurium glass based electronics. Even if a fund tried this, the price would crash as soon as Intel or Samsung announced they could no longer get material. Perhaps then someone will create a tellurium ETF.
In any case, I'm going to try and find out who is producing tellurium in the U.S. right now. If you know, please comment. The USGS does not identify the major producers; it just says that they are doing so.
Next week I'm going to tell you about the military's use of tellurium and selenium and their use in solar energy conversion. Tellurium and selenium chemical compounds are sensitive to light over a large range of wavelengths. Their electronic properties can be changed by sunlight or by infrared (heat) light. Glasses made from these elements can even focus infrared light.
Next time you're at an air show or reading about heat-seeking missiles, just take a look at the dome on the front of such a missile. That's a lot of selenium/tellurium glass.
Did I tell you, by the way, that my technical supervisor when I worked at ITT Advanced ElectroOpical Laboratory in San Fernando, California in the 1960s was Doctor Richard Orthuber, who, in 1937, invented the technology for the heat seeking guided missile? It was based on cadmium sulphide and cadmium telluride's ability to change its electrical properties when heat from an object such as the exhaust of an aircraft engine was focused upon a device made from it.
Tellurium has been around a long time, but it's just now breaking its way into the public's awareness. I don't think it will take nearly as long for tellurium to become a good investment as it took for the phase change memory to be mass marketed.