by Kevin Bonsor
On your next trip to the local shopping mall, stop by one of the jewelry stores. Notice the diamond jewelry that takes up the majority of the showcase, and the number of people hovering over the counters trying to pick out a diamond for their loved one. There will surely be a salesperson explaining the "4 Cs" -- cut, clarity, carat and color -- to a young shopper, and explaining why one diamond is better than the one right next to it. Why all the fuss over diamonds?
Diamonds are just carbon in its most concentrated form. That's it -- carbon, the element that makes up 18 percent of the weight of your body. In many countries, including the United States and Japan, there is no other gemstone as cherished as the diamond, but in truth, diamonds are no more rare than many other precious gems. They continue to demand higher market prices because the majority of the diamond market is controlled by a single entity.
In this article, we will track a diamond from the time it is formed to when it reaches the Earth's surface. We will also examine the artificial rarity created by the diamond cartel, De Beers, and briefly discuss the properties of these gems.
Carbon is one of the most common elements in the world, and is one of the four essentials for the existence of life. Humans are more than 18-percent carbon. The air we breathe contains traces of carbon. When occurring in nature, carbon exists in three basic forms:
Temperatures can reach 1,652 F (900 C) in Archean cratons. These are common places for diamonds to form. Archean cratons are stable, horizontal geological formations created billions of years ago that have been unaffected by major tectonic events, according to Rex Diamond Mining Corp. These cratons are found in the center of most of the seven continents (most tectonic activity takes place around the edges).
Diamonds form about 100 miles (161 km) below the Earth's surface, in the molten rock of the Earth's mantle, which provides the right amounts of pressure and heat to transform carbon into a diamond. In order for a diamond to be created, carbon must be placed under at least 435,113 pounds per square inch (psi or 30 kilobars) of pressure at a temperature of at least 752 degrees Fahrenheit (400 Celsius). If conditions drop below either of these two points, graphite will be created. At depths of 93 miles (150 km) or more, pressure builds to about 725,189 psi (50 kilobars) and heat can exceed 2,192 F (1,200 C).
Most diamonds that we see today were formed millions (if not billions) of years ago. Powerful magma eruptions brought the diamonds to the surface, creating kimberlite pipes. On the next page, you'll find out about these pipes.
Diamonds are not exclusive to Earth. Scientists believe that diamonds may one day be found on the moon. Samples of rock brought back from the moon indicate that carbon is 10 times more abundant in the Earth's crust than the moon's, according to the Artemis Project, a group whose goal is to establish a permanent moon community. But this group believes that there may be diamonds under the moon's surface that Apollo astronauts were unable to detect. There is also some scientific evidence that diamonds may be found in larger abundance on Neptune and Uranus. Neptune and Uranus contain a lot of the hydrocarbon gas methane. Researchers at the University of California, Berkeley, have shown that focusing a laser beam on pressurized liquid methane can produce diamond dust. Neptune and Uranus contain about 10-percent to 15-percent methane under an outer atmosphere of hydrogen and helium. Scientists think that this methane could possibly turn to diamond at fairly shallow depths.
Kimberlite is named after Kimberly, South Africa, where these pipes were first found. Most of these eruptions occurred between 1,100 million and 20 million years ago.
Kimberlite pipes are created as magma flows through deep fractures in the Earth. The magma inside the kimberlite pipes acts like an elevator, pushing the diamonds and other rocks and minerals through the mantle and crust in just a few hours. These eruptions were short, but many times more powerful than volcanic eruptions that happen today. The magma in these eruptions originated at depths three times deeper than the magma source for volcanoes like Mount St. Helens, according to the American Museum of Natural History.
The magma eventually cooled inside these kimberlite pipes, leaving behind conical veins of kimberlite rock that contain diamonds. Kimberlite is a bluish rock that diamond miners look for when seeking out new diamond deposits. The surface area of diamond-bearing kimberlite pipes ranges from 2 to 146 hectares (5 to 361 acres).
Diamonds may also be found in river beds, which are called alluvial diamond sites. These are diamonds that originate in kimberlite pipes, but get moved by geological activity. Glaciers and water can also move diamonds thousands of miles from their original location. Today, most diamonds are found in Australia, Borneo, Brazil, Russia and several African countries, including South Africa and Zaire.
Diamonds are found as rough stones and must be processed to create a sparkling gem that is ready for purchase. In the next section, you will learn how a diamond is cut and polished.
As mentioned before, diamonds are the crystallized form of carbon created under extreme heat and pressure. It's this same process that makes diamonds the hardest mineral we know of. A diamond ranks a 10 on the Mohs Hardness Scale (see below). It can be anywhere from 10 to hundreds of times harder than a mineral ranked nine on the Mohs scale, such as corundum. Corundum is a class of minerals that includes rubies and sapphires.
It is the molecular structure of diamonds that makes them so hard. Diamonds are made of carbon atoms linked together in a lattice structure. Each carbon atom shares electrons with four other carbon atoms, forming a tetrahedral unit. This tetrahedral bonding of five carbons forms an incredibly strong molecule. Graphite, another form of carbon, isn't as strong as diamond because the carbon atoms in graphite link together in rings, where each atom is only linked to one other atom.
There are special techniques that are used to cut and shape a diamond before it gets to the jewelry store. Diamond cutting creates the facets that you see in the diagram above. Diamond cutters use these four basic techniques:
Diamonds are judged on several factors that determine their beauty. Most diamonds never reach the consumer market because they are too flawed. Often, these diamonds are used for industrial purposes -- as an abrasive, for drill bits or for cutting diamonds and other gems. If you've ever purchased a diamond, you've heard of the "4 Cs:"
Other unique qualities of the diamond include its transparency, luster and dispersion of light. A diamond that is created from 100-percent carbon will be completely transparent. Diamonds often contain other elements that can affect the color. Although we often think of diamonds as being clear, there are also blue, red, black, pale green, pink and violet diamonds. These colored diamonds are the truly rare ones.
The Mohs Scale is used to determine the hardness of solids, especially minerals. It is named after the German mineralogist Friedrich Mohs. The scale reads as follows, from softest to hardest:
Source: Kingzett's Chemical Encyc.
Diamonds are made in the molten magma deep inside the Earth. Only nature can create diamonds, but it is people who have created the artificial rarity that has spurred demand for these gems. Carbon is one of the most common elements in the world, and diamonds are a form of carbon. Naturally occurring diamonds are no more rare than many other precious gems. The truly rare transparent diamonds are those rated as flawless, meaning that they don't have the slightest imperfection.
Prior to the 1930s, diamond rings were rarely given as engagement rings. Opals, rubies, sapphires and turquoise were deemed much more exotic gems to give as tokens of one's love, according to the book "Twenty Ads that Shook the World," by James B. Twitchell. Twitchell goes on to describe how De Beers changed the world diamond market.
This idea of connecting diamonds to romance was captured in a brilliant ad campaign begun in the 1940s, causing demand for diamonds to increase. Surely you've heard the De Beers advertisement telling you that "A Diamond is Forever." This ad campaign, which was created by the N.W. Ayer advertising agency in 1947, changed the diamond market. In 2000, Advertising Age magazine named the ad campaign the slogan of the 20th century. De Beers infiltrated Japan with the same ad campaign in the 1960s, and the Japanese public bought into the idea as much as the Americans did.
Later ads by De Beers told consumers to hold onto their family's diamond jewelry and to cherish them as heirlooms -- and it worked. This eliminated the aftermarket for diamonds, which further enabled De Beers to control the market. Without people selling their diamonds back to jewelers or to other people, the demand for new diamonds increased.
There are fewer than 200 people or companies authorized to buy rough diamonds from De Beers. These people are called sightholders, and they purchase the diamonds through the Central Selling Organization (CSO), a subsidiary of De Beers that markets about 70 percent to 80 percent of the world's diamonds. De Beers sells a parcel of rough diamonds to a sightholder, who in turn sends the diamonds to cutting facilities and then to distributors.
There are rough diamonds sold outside the CSO. These diamonds come from small producers in Australia, Russia and some African countries. The cost of these diamonds is still largely influenced by the prices set by the CSO.
Diamonds are the most coveted of all precious gems, as is witnessed by the extremely high demand for them. While this has not always been the case, diamonds are nonetheless exquisite gems that go through a long, tedious refining process from the time they are pulled from the ground to when you see them in the jewelry store. And, while some of the mystique of diamonds may be gone -- they're just carbon, after all -- the diamond will likely continue to be a highly coveted jewel, because, well, "A Diamond is Forever."