How Diamonds are Formed

How Diamonds are Formed

Most of us think of diamonds as natural wonders formed deep within the Earth many years ago. However, only a few of us realize how exactly it is that natural diamonds were formed, or that there are even diamonds formed in space.

At the same time, some still believe that diamonds were formed from coal, or think that lab-grown diamonds are not real diamonds. This article answers the most popular questions about diamonds, how coloured diamonds were formed, whether synthetic diamonds are real diamonds, and which of them can be the best value for your buck.

How Long Does a Diamond Take to Form?

When it comes to mined diamonds, the process of their formation took place many millions or even billions of years ago. This process was interrupted on occasion due to changes in pressure or temperature, and resumed once the conditions for diamond growth were back again.

Today, scientists can date the period when diamonds were formed, but are still unable to determine how long it took for natural diamonds to take form. However, it is widely believed that the process of formation of natural diamonds could take millions of years.

How Are Natural Diamonds Formed?

Most natural diamonds are formed deep down within the Earth under extreme heat and pressure conditions. However, this is not the only way of forming natural diamonds, which can also be found at impact sites where the Earth was hit by asteroids, and even in space.

How Are Diamonds Made from Coal?

Although both diamonds and coal are formed underground at high pressures and temperatures and are both made of carbon, their similarities end there.

Unlike diamonds, coal includes not only carbon but also organic plant residue. Coal is formed much closer to the Earth’s surface, which is why it also contains plant materials. Meanwhile, diamonds are composed entirely of carbon and were formed much deeper down, transported to the Earth’s surface through volcanic pipes.

How Are Diamonds Made from Carbon?

Natural diamonds are pure carbon crystals formed under temperatures above 2,000 degrees Fahrenheit and at a pressure exceeding 725,000 pounds per square inch. For comparison, this pressure is 50,000 times more than the atmospheric pressure at the Earth’s surface.

Such extreme pressure and heat have transformed crystalline carbon, also known as graphite, into what we know as natural diamonds. As a result of this transformation, the crystal structure of graphite is changed from hexagonal into isometric so that the carbon atoms in diamonds are bonded the same way in all directions.

How Are Diamonds Formed in the Earth?

Natural diamonds were formed within the Earth under pressure and heat. After billions of years of their formation, natural diamonds were elevated closer to Earth’s surface through so-called kimberlite pipes, which have received their name after the town of Kimberly in South Africa.

Kimberlite pipes result from magma eruption. When magma moves under pressure towards the Earth’s surface, it chooses paths with the least resistance, forming a carrot-like kimberlite pipe. These pipes contain igneous rocks known as kimberlites, which are the major source of natural diamonds.

Some diamonds can be found at places where the Earth was hit by asteroids in Siberia and Arizona, known as impact sites. Meanwhile, other diamonds were discovered in the so-called subduction zones created as a result of the movement of tectonic plates. However, diamonds coming from meteorite craters and impact sites are smaller or of lower purity, making them more suited for industrial use than jewellery.

Diamond Formation in Space

Meteorites create not only craters full of diamonds, but also diamonds formed on other planets. NASA researchers have been able to find large amounts of diamonds in meteorites such as the Allen Hills meteorite from Mars, found in Antarctica. Space-born diamonds are even smaller than those formed in meteorite craters and are not used in jewellery, but are nevertheless real diamonds of extraterrestrial origin.

How Are Coloured Diamonds Made?

The traditional “clear” diamonds, sometimes referred to as colourless or “white” diamonds, are graded based on their lack of colour from D to Z. On this scale, D represents the highest colour grade assigned to the best diamonds, which appear colourless, while Z is the lowest grade for diamonds with a light yellow hue. Meanwhile, most coloured diamonds are valued for the intensity of their colour, resulting from impurities.

How Are Black Diamonds Formed?

Black colour diamonds are very rare and unique. Unlike other coloured diamonds, black diamonds are entirely opaque, and are not graded for their colour intensity, as they are entirely black.

Black diamonds are formed under the Earth’s surface, similar to other colourless and coloured diamonds. Their exceptional black hue results from their crystal structure, which absorbs most light, as well as from inclusions of graphite that gives the stones their metallic black appearance. Black diamonds may have white or gray inclusions, making them even more rare and unique.

How Are Red Diamonds Formed?

There are only 20-30 red diamonds in the world, making them the rarest among coloured diamonds. Their exceptional red hue doesn’t result from inclusions, but comes from a unique crystal structure emerging in the process of their formation.

The crystal structure of red diamonds changes how the light passes through these stones and creates an incredible red colour. Even though most red diamonds are a half-carat in size, these are the ones which are the most expensive.

How Are Pink Diamonds Formed?

Similar to red diamonds, pink diamonds receive their romantic hue from their crystal structure, which was changed in the process of formation. This special configuration of carbon atoms alters the way the light passes through the crystals and creates a pink colour appearance.

The best pink diamonds with the most intense hue are found in Argyle Mine in Australia. Pink diamonds are incredibly rare, and considered highly-valued coloured diamonds.

How Are Blue Diamonds Formed?

Unlike red and pink diamonds, which receive their unique hue from the crystal structure, blue diamonds get their colour from the chemical element known as boron. Boron replaces some of the carbon atoms within the diamond structure, producing various shades of blue.

Blue diamonds can be found in Australian, Indian, and South African mines. Although they are less expensive than their pink and red counterparts, blue diamonds are also very rare, boasting a high cost per carat.

How Are Yellow Diamonds Formed?

Yellow and brown diamonds get their hue from another chemical element called nitrogen. The nitrogen absorbs blue light and reflects yellow colour.

Yellow diamonds are the most common and make for approximately half of the market of coloured diamonds. The most sought-after yellow diamonds are known as Canary Diamonds, which possess a pure yellow hue.

Synthetic Diamond Formation

Unlike natural diamonds, which can take millions of years to form, synthetic diamonds can be grown in labs in a month. The process of growing synthetic diamonds uses electric power to create necessary pressure and heat and resembles the way natural diamonds were formed deep beneath the Earth’s surface.

Methods for Growing Diamonds in Labs

Today, there are two lab processes for growing diamonds known as Chemical Vapor Deposition (CDV) and High-Pressure-High-Temperature (HPHT) processes.

The CVD process uses carbon-rich gases in a heated chamber to form a diamond on seed diamond crystals. Meanwhile, the HPHT process closely resembles how mined diamonds were formed in nature. In the HPHT process, natural graphite is subjected to extreme pressure and temperature in a lab, turning graphite into a diamond.

How Lab-Grown Diamonds Compare to Mined Diamonds

Although the first lab-grown diamonds were crude and could only be used for industrial purposes, modern lab methods produce diamonds which are practically indistinguishable from mined stones. Lab-grown diamonds are graded by GIA and IGI using the same 4C grading system as mined diamonds.

Today, lab-grown diamonds are so close to mined

stones that the U.S. Federal Trade Commission (FTC) has now dropped the word “natural” when defining a diamond. The FTC has based its decision on scientific facts, and its conclusion is that lab-grown diamonds have ‘essentially the same optical, physical and chemical properties as mined diamonds.’

Which Diamonds Are the Best Value for Money?

When making a comparison among colourless mined diamonds, coloured diamonds, and lab-grown stones, multiple factors should be considered. For example, buying a diamond for an engagement ring is different from purchasing gemstones for investment purposes.

Thus, lab-grown diamonds offer significant savings in price that can be spent on weddings or purchasing a larger stone with better 4C characteristics. Also, lab-grown diamonds can be the perfect choice for those who are looking for 100% ethical, eco-friendly jewellery.

On the other hand, mined diamonds are natural wonders that can be more appealing to those looking for unique and special stones. Although they are more expensive than lab-grown gemstones, mined diamonds are far rarer, and thus keep their value better. Meanwhile, coloured high-quality diamonds are the rarest stones, and are a frequent choice of investors.

Contact Us

Searching for high-quality diamonds and diamond jewellery is a never-ending adventure full of bright and glittering discoveries. If you are looking for ethically-mined colourless, coloured, and lab-grown diamonds, you can count on Barry’s Jewellers at Burlington to help you on your journey.

Call Barry’s Jewellers at 866.651.0876, send us an email at info@barrysjewellers.com ,or get in touch through our website and our friendly and professional consultants will be with you every step of the way to help you find your best diamond.



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