Diamonds of the laboratory
Workers leaving the diamond mines of South Africa are carefully searched before they are allowed to go home. The mine owners fear that some of the precious gems will be smuggled out, hidden in the clothing, or even inside the mouths, ears or noses of the miners. For generations men have dug deep beneath the earth's surface, searching for the stones that can glow with a thousand inner fires. History's pages are alight with this blaze: the Spanish conquistadors proudly returned home from Mexico and Peru with a wealth of emeralds; a cardinal who was out of favor bought a diamond necklace for Queen Marie Antoinette; a diamond was used as security for a loan from the Netherlands in the days of the French Revolution. The crowns and scepters of hundreds of royal dynasties have been encrusted with precious gems. Pirates have sailed the seas, stealing and then burying treasures of gold and jewels.
Legends and stories have grown up around precious stones - from Aladdin's cave in The Arabian Nights to the curse on the person who dared to wear the Hope Diamond. In ancient times diamonds were supposed to have the power to prevent insanity. In periods of violence and treason many people believed that wearing a diamond would work as an antidote to poison. In the Middle Ages possession of this jewel was supposed to keep the peace between husband and wife. That custom, only slightly changed, is still in effect. The diamond in the engagement ring is a symbol of everlasting love.
Rubies, emeralds, diamonds and sapphires remain the outward signs of wealth and success. In a changing world this does not change. A few years ago a popular song was entitled "Diamonds Are a Girl's Best Friend." The lyrics were simply restating the well-known fact in a witty way.
Take away the legends and glamor that surround precious gems, and what do you have? Minerals in the form of crystals. That does not sound very pretty, nor do the crystals look pretty at first glance. Until they are cut and polished the fire within is hidden.
About a hundred years ago a South African child was sent out on the veldt or plain to gather wood. He saw a glittering pebble lying on the ground. The boy picked it up and put it in his pocket, where it rattled around along with pieces of string, bits of candy and old spelling lists. A few days later he took out the pebble and gave it to his little sister as a toy. A keen-eyed visitor noticed the stone one day, and asked for it as a gift, without telling the innocent children why he wanted it. He later sold it as the genuine diamond which it was.
Although children from that day to this have been bringing home shiny stones in the hope that they were diamonds, few if any have succeeded in finding the real thing. jewels are called precious gems because they are as rare as they are beautiful. That is what makes them so valuable.
As everyone, rich or not, likes to have beautiful things, imitations of the lovely crystals must serve as the poor man's Hope Diamond. Costume jewelry is not a twentieth-century fashion. Back in 3000 B.C. there were necklaces, bracelets and brooches containing early substitutes for precious stones.
Over the centuries many kinds of substitutes have been tried. Whether you go into the five-and-ten-cent store or the most expensive shop in town, you can find copies of every single precious jewel. The cheapest are known as "imitation" jewels. These can be made of anything at all. They simply resemble the natural gem. They are not like it in terms of hardness, weight, brilliance or chemical composition. Glass is used most often, with coloring added when an emerald, ruby or sapphire is to be imitated. There are also a number of common natural stones which look something like valuable ones and can be used as substitutes. These are set in slightly more expensive costume jewelry. In the next price range you find jewels which are real, but which are not in their natural form. Tiny fragments of real stones, left over when large emeralds or sapphires are cut, are treated to make them stick together.
Jewelers, customers and scientists have not been fully satisfied with these substitutes.
"It should be possible to make a precious stone that not only looks like the real thing, but that is the real thing," said a chemist many years ago. "The only difference should be that one crystal would be made by man, the other by nature."
At first this did not seem like a particularly hard task. Scientists began to try making synthetic diamonds toward the end of the eighteenth century. It was at this time that a key scientific fact was discovered: diamonds are a form of carbon, which is a very common element. Graphite, the black mineral that is used for the "lead" in your pencil, is made of it, too. The only difference, we know today, is that the carbon atoms have been packed together in a slightly different way. The chemists were fired with enthusiasm: Why not change a cheap and plentiful substance, carbon, into a rare and expensive one, diamond?
You have probably heard about the alchemists who for centuries tried to turn plain lead or iron into gold. They failed, because gold is completely different from lead or iron. Transforming carbon into diamonds, however, is not illogical at all. This change takes place in nature, so it should be possible to make it happen in the laboratory.
It should be possible, but for one hundred and fifty years every effort failed. During this period, nonetheless, several people believed that they had solved the diamond riddle. One of these was a French scientist who produced crystals that seemed to be the real thing. After the man's death, however, a curious rumor began to go the rounds. The story told was that one of the scientist's assistants had simply put tiny pieces of genuine diamonds into the carbon mixture. He was bored with the work, and he wanted to make the old chemist happy.
The first real success came more than sixty years later in the laboratories of the General Electric Company. Scientists there had been working for a number of years on a process designed to duplicate nature's work. Far below the earth's surface, carbon is subjected to incredibly heavy pressure and extremely high temperature. Under these conditions the carbon turns into diamonds. For a long time the laboratory attempts failed, simply because no suitable machinery existed. What was needed was some sort of pressure chamber in which the carbon could be subjected to between 800,000 and 1,800,000 pounds of pressure to the square inch, at a temperature of between 2200°F and 4400°F.
Building a pressure chamber that would not break under these conditions was a fantastically difficult feat, but eventually it was done. The scientists eagerly set to work again. Imagine their disappointment when, even with this equipment, they produced all sorts of crystals, but no diamonds. They wondered if the fault lay in the carbon they were using, and so they tried a number of different forms.
"Every time we opened the pressure chamber we found crystals. Some of them even had the smell of diamonds," recalls one of the men who worked on the project. "But they were terribly small, and the tests we ran on them were unsatisfactory."
The scientists went on working. The idea was then brought forward that perhaps the carbon needed to be dissolved in a melted metal. The metal might act as a catalyst, which means that it helps a chemical reaction between two other elements to take place.
This time the carbon was mixed with iron before being placed in the pressure chamber. The pressure was brought up to 1,300,000 pounds to the square inch and the temperature to 2900° F. At last the chamber was opened. A number of shiny crystals lay within. These crystals scratched glass, and even diamonds. Light waves passed through them in the same way as they do through diamonds. Carbon dioxide was given off when the crystals were burned. The density or weight was 3.5 grams per cubic centimeter, as is true of diamonds. The crystals were analyzed chemically. They were finally studied under X rays, and there was no longer room for doubt. These jewels of the laboratory were not like diamonds; they were diamonds. They even had the same atomic structure. The atoms making up the molecule of the synthetic crystal were arranged in exactly the same pattern as they are in the natural.The scientists did not rush out to the jewelers to have these crystals set in rings or tiaras to rival Queen Elizabeth's. Instead, they rushed the laboratory-made diamonds into industry, which is using millions of carats a year. Diamonds are harder than any other substance on earth. In the days before X rays and microscopic analysis people used to decide whether a gem was a diamond by attempting to scratch their names with it on a windowpane. If that worked, they went on to a test that is still considered pretty good: They tried to scratch a real diamond (if they had one) with the suspected crystal. Of course, there is little to be gained by scratching diamonds or etching your name on a windowpane, but this hardness makes diamonds particularly useful in grinding wheels and high-speed cutting tools.
Dental drills and the giant drills that bore through rock in search of oil or minerals need industrial diamonds. Diamond-cutting wheels are used to cut concrete blocks and marble. Superfine electric wiring used in television sets, X ray machines, radar and rockets is made by drawing heavy wire through a hole in a diamond die. In much the same way, yarns are spun out of tungsten and molybdenum. Fabrics made out of these yarns are being tested for use in space suits.
The military and space uses of industrial diamonds are so important that the Army Signal Corps and the Air Force Systems Command are making their own synthetic diamonds for use in research projects.
Africa, which supplies about 95 percent of the world's industrial diamonds, has often been torn by strife, and imports have been endangered. The United States has no diamond mines beneath the earth, so it is fortunate that we have some above the ground in the laboratory.
Chemists are already learning how to do tricks with synthetic diamonds. When tiny amounts of boron, beryllium or aluminum are added to the carbon, the diamonds become semiconducting. This means that an electric current can pass through them, making them suitable for use in transistors and other electronic devices. As less than one percent of natural diamonds are semiconducting, this discovery is most important. Scientists believe that the famous Hope Diamond is a semiconductor, but no one suggests destroying this beautiful gem for its electrical qualities.
The trail leading to the perfect synthetic diamond has not yet been followed to the very end. Better ways of transforming graphite into diamonds are still being worked out. The General Electric Research Laboratory recently announced discovery of a method that does the job in a few thousandths of a second. It does not require a metal catalyst either. The secret lies in an improved pressure chamber that can achieve pressures of three million pounds to the square inch at temperatures above 9000°F. Other experiments are also still going on.
"The jewels we have made are diamonds," says a physicist, "but they are not very beautiful. Natural diamonds range in color from white to black, with the white or blue-white favored as gems. Most of ours are on the dark side, and are quite small."
Not one compares in size with the famed Cullinan Diamond, which originally weighed 3,025-3/4 carats. It takes 142 carats to make an ounce, so a little figuring will show you that the diamond weighed a little more than one pound and 5 ounces. The Cullman was cut into 9 large and 7 small stones. Even at that, the two biggest ones, at 516 and 309 carats respectively, remain the largest diamonds in the world today. Another famous diamond, the Regent or Pitt, which weighed 136 carats, was once mounted by Napoleon on the hilt of his sword. These world-famous gems are, of course, too big for normal use. No girl could wear an engagement ring with a stone of 100 or more carats. She would have to be built like a stevedore to be able to raise her hand. The synthetic stones, however, look too insignificant.
In the future scientists may succeed in producing synthetic diamonds lovely enough to be used as gems. In the meantime, a diamond substitute has been discovered. As this gem stone is not the same as a diamond chemically or physically, it is technically an imitation. The men who produced it object violently to this description.
"It is a completely new jewel," they maintain, " a crystal with all the fire and brilliance of the most beautiful gems found in nature. This is the first man-made gem. It only exists in the laboratory. You could not go out and dig one up."
Strange as it seems, this diamondlike jewel was discovered by scientists working for the National Lead Company, one of the largest paint manufacturers in the United States. Their aim was to improve the paint, not to create gems. White paint is made with a chemical called "titanium dioxide." The chemists believed that a careful study of the crystal of titanium dioxide would tell them many new things about the chemical. However, single crystals had never been found in nature. They decided, therefore, to make one, using a high-temperature furnace. The crystal that emerged from the furnace was breathtakingly beautiful.
"That would certainly look terrific in a ring!" exclaimed one of the laboratory assistants.
Everyone could see that he was right. A new jewel was born, which had even more fire and brilliance than a diamond. It had, however, one major drawback. Titanium has a characteristic greenish-yellow cast which marred the beauty of the stone. A slight change in the chemical composition might solve that, thought the chemists. Like cooks deciding whether to add a touch of vanilla or peppermint extract to the cookie batter, the scientists tried adding a pinch of this element and a touch of that. And in time they discovered that a combination of titanium and strontium produced a brilliant, clear white crystal.
This stone, which has been named "Fabulite," is much softer and heavier than its natural brother. This makes it unsuitable as a substitute for industrial diamonds. Some uses for the man-made gem have been found in making infrared lenses. Mostly it is intended for wear as a jewel. "Fabulite" can be cut exactly like a diamond, and it costs much less.
"We go nature one better," boasts one of the technicians who developed the gem. "If you dig for diamonds or rubies or sapphires you will turn up thousands of imperfect stones for every one that is good. But all of our jewels are perfect. There is no second best. Every one is the best."
(From The artificial world around us, by Lucy Kavaler)