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Diamonds are the hardest naturally forming material on Earth, renowned for their beauty, strength, and durability. They have been known and hoarded by humans for thousands of years, and their name comes from the Greek word for invincible.
These stones come from deep within the Earth’s crust, formed there by the incredible pressure and relatively manageable temperatures. They form beneath the continental crust, from pure carbon. This carbon may either come from exclusively non-organic sources, organic sources, or a blend of the two. Diamonds formed from inorganic carbon are called harzburgitic diamonds, while those formed from some amount of organic carbon are called eclogitic diamonds.
Diamonds form at depths of around 90 miles (150km), over millions and millions of years. The temperature at which they form is in the range of 2,000° Fahrenheit (1,100° Celsius) — too much hotter than this and the conditions are no longer suitable for their formation. Most are over a billion years old by the time they reach the Earth’s surface, with some diamonds being over three billion years in age — not much younger than the Earth itself.
The stones come to the surface when magma from far below the Earth’s surface begins coming up. Since they are found at such incredible depths — three to four times deeper than the depth at which a normal volcano originates — magma upsurges deep enough to bring them to the surface are relatively rare. Once this magma cools, it forms a rock known as kimberlite — or sometimes lamproite — which may be used as an indicator that diamonds may be found in that area.
By mining into one of these kimberlite dikes, or kimberlite pipes, diamonds may be uncovered. Of course, the presence of kimberlite does not necessarily guarantee that the precious stones will be present, simply that the volcanic upsurge originated at sufficient depth that diamonds could have formed. Often these kimberlite dikes will erode over time, and the gems will be carried away with the sediment, to accumulate in basins somewhere.
While kimberlite dikes are the most common place where diamonds can be found, others also exist. In some cases, glacial action may pick up diamonds and transport them many hundreds of miles, leaving them behind in their path or when they eventually melt. This has led to stones being found in locations that geologically were not appropriate, but not in sufficient quantities to make tracking glacial paths a viable method of hunting.
Extremely small diamonds may also be formed under certain extraordinary conditions. Such microdiamonds are sometimes formed, for example, when meteors strike the Earth’s surface. Although they are not of sufficient size to be particularly valuable, they do serve as a reliable indicator of impact craters from meteors.
For many centuries India was the world’s top source of diamonds, but eventually these sources were mostly depleted. In the modern world, nearly half of all those mined come from mines in southern and central Africa. The bulk of these mines are owned and operated by various companies of the De Beers Group, which is responsible for more than 40% of diamonds by value worldwide, and has held a virtual stranglehold on the world market since its formation in the 1860s. Large-scale mines also exist in Brazil, Australia, Siberia, and parts of Canada. Once mined, these diamonds travel the world to be cut and polished to create the beautiful gems we are all familiar with. Most cutting takes place in a few areas of the world, most notably New York, Antwerp, and Tel Aviv.
Frequently Asked Questions
How are diamonds formed?
Diamonds are formed deep within the Earth's mantle under conditions of intense heat and pressure, about 90 miles (150 kilometers) or more below the surface. Carbon atoms bond in a crystal structure due to these extreme conditions, which can take 1 billion to 3.3 billion years, according to the Gemological Institute of America. Volcanic eruptions then bring these diamond-containing rocks closer to the Earth's surface, where they can be mined.
What is the main source of diamonds?
The primary source of natural diamonds is kimberlite pipes, which are volcanic rock formations that serve as the most significant reservoirs for diamond deposits. These pipes are found in regions known for diamond mining, such as South Africa, Russia, and Canada. For instance, the Kimberley Mine in South Africa is one of the most famous sources, giving the name 'kimberlite' to these diamond-bearing rocks.
Can diamonds be found anywhere in the world?
Diamonds are not found everywhere; they are concentrated in certain parts of the world where the geological conditions were right for their formation. The leading diamond-producing countries include Russia, Botswana, Canada, Angola, and South Africa. Together, these countries account for the majority of the world's diamond production, with Russia and Botswana being the largest producers, according to the latest statistics from the Kimberley Process Certification Scheme.
Are all diamonds used in jewelry?
Not all diamonds are suitable for jewelry. Only about 20% of mined diamonds meet the quality standards for use in jewelry due to their clarity, color, and size, and these are referred to as gem-quality diamonds. The remaining 80% are used in industrial applications, such as cutting, grinding, and drilling, because of their exceptional hardness and thermal conductivity, as reported by the World Diamond Council.
How do lab-grown diamonds compare to natural diamonds?
Lab-grown diamonds are chemically, physically, and optically identical to natural diamonds but are created in controlled laboratory environments using high-pressure high-temperature (HPHT) or chemical vapor deposition (CVD) methods. They can be produced in a matter of weeks rather than billions of years. While they offer a more sustainable and ethical alternative, natural diamonds often carry a higher market value due to their rarity and the historical and emotional value associated with them.