This question really covers several topics: How are diamonds formed? What is the geographic origin of my diamond? How do I know whether my diamond is conflict-free?
How are Diamonds Formed?
Not all diamonds are created the same way. They come from three primary sources: earth, laboratories, and outer space.
Earth
Most naturally occurring diamonds were created over 100 miles below the Earth’s surface, in the upper mantel. Billions of carbon atoms joined under extremely high temperature and high pressure. The diamonds reached the Earth’s surface through volcanic eruptions, but not just any eruptions. In order to throw the formed diamonds all the way to the surface fast enough and strong enough to prevent the carbon atoms from reforming into graphite, the spew had to begin below the diamonds and travel 20 to 50 mph. Eruptions like this have not been witnessed in recent times. Without the perfect eruption, the diamond remains hidden at a depth where current technology can’t reach it.
Other conditions must be “perfect,” too. Even a one-carat diamond requires billions of carbon atoms to bond, and all of those atoms must be carbon to create a colorless diamond. The slightest quirk creates a colored diamond: a bit of boron makes a blue diamond; nitrogen makes a yellow diamond; natural radiation form nearby rocks trap electrons to create a green surface color; pink or red shades are thought to be due to changes to the electron structure during the voyage to the surface.
While diamonds can’t be dated, the materials found around them can. The youngest diamonds on Earth appear to be hundreds of millions of years old, and older ones stretch back billions of years. The carbon atoms that composed the diamonds were previously parts of the mantle or sediment from animals, plants, and shells. As tectonic plates shifted, material on the surface was pulled downward, into the diamond producing zone.
Laboratories
“Manmade diamonds” are actually more prevalent than natural diamonds. Since 1950s, laboratories have manufactured diamonds, either by forcing carbon atoms to juncture under extreme heat and pressure or by reducing methane gas. Depending on the particular company’s formulation, the process can take days to weeks. Though the process is sped up, diamond formation is still a sensitive process where conditions fluctuate, yielding diamonds just as flawed and unique as those found in nature.
Outer Space
The pressure and temperature required to create diamonds is not limited to subterranean Earth. A meteorite’s impact can create diamonds. Meteors colliding with other objects in space create diamonds embedded in the meteors. Scientists look for microscopically small nano-diamonds to indicate where meteorites might have hit Earth.
Even stars create diamonds. Star dust contains tiny bits of diamonds, the oldest diamonds in existence. And when a star uses up all of its energy and dies, it can become a diamond. White dwarf BPM 37093 (nicknamed Lucy after the Beatles’ song “Lucy in the Sky with Diamonds”) is composed of mostly carbon with a thin coating of hydrogen and helium gases. Lucy is 10 billion trillion trillion carats in size—roughly the size of Earth’s moon.
Our own solar system’s sun is believed to be heading in the same direction—five to seven billion years from now it will cool down and become a huge diamond as well.
Where Do Diamonds Go?
Diamonds are most often associated with jewelry, but their strength is highly sought in a variety of industrial applications: to cut, polish, and grind hard surfaces; to manipulate concrete, metal, ceramic, computer chips, eyeglasses, stones, and other gems; and as parts of surgical blades, heat spreaders, and specialty windows.
Even though 80% of the natural diamonds mined each year go toward industrial purposes, four times as many diamonds are synthetically created to also go toward industrial use. Approximately 25 million carats of natural diamonds go toward jewelry each year, another 80 million carats of natural diamonds go toward industrial use, and an additional 570 million carats of lab-manufactured synthetic diamonds are created for industrial purposes.
This does not mean synthetic diamonds should not be considered for jewelry. Prices are much lower than natural diamonds, and the quality can be worse or better than a natural diamond.
Where is My Diamond From?
Natural diamonds are mined in approximately 25 countries across five continents. However, Africa, Russia, and Canada account for more than 90% of the world’s natural gem-quality diamond production. Combined production in these three locations exceeds 80 million carats of gem-quality diamonds per year, which is equal to almost 17 metric tons of diamonds. Africa accounts for more than 50% of the global diamond mining industry, with majority of the diamonds mined in just four countries: Botswana, Angola, South Africa, and Congo.
Australia, Congo, and Russia are the largest producers of industrial quality diamonds, mining 60 million carats per year (or 75% of the global non-synthetic production).
Thanks to the Kimberly Process, diamonds mined starting in 2003 carry certificates indicating the location where the diamond rock was unearthed. Before 2003, diamond purchasers might have no indicated of their diamonds’ origins, but now they can even name the particular mine.
The United States is the largest producer of synthetic diamonds in the world. It accounts for almost 50% of the world’s annual production. The US is followed by Russia, South Africa, Ireland, and Japan, together accounting for another 40% of the global production of synthetic diamonds.
What is a Blood Diamond?
A “blood diamond” (also known as conflict diamond, war diamond, dirty diamond, hot diamond, or converted diamond) is mined or produced in unethical conditions, including in war zones to finance insurgencies.
In 2003, the UN-backed Kimberley Process began requiring participating countries to certify that their exported diamonds were conflict-free. According to the World Diamond Council, this program has been very successful, with 99% of the world’s diamond supply certified as conflict-free. Some other estimates are not as optimistic, but the Kimberly Process does seem to work—the amount of blood diamonds in the market is estimated to have dropped from 15% before the Kimberly Process was introduced to less than 5% today.
Some retailers also offer “conflict neutral” diamonds. The retailer or the consumer makes a donation to a relevant charity, with the expectation that the good works promoted by that donation help balance against the negative works in the diamond industry.
An alternative to purchasing a new diamond is to “recycle” a diamond—purchase or be gifted someone else’s older diamond. While there is always the chance that the diamond was originally mined as a blood diamond, at least reusing it does not add to the funding of recent conflicts. A reused family stone carries the additional bonus of sentimental value.