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Pit

Pit Type of diamond blemish that appears as a tiny opening or indentation on the surface of a diamond.

A pit is a type of diamond blemish that appears as a tiny surface indentation or opening on the diamond’s exterior. These minute imperfections can be caused by natural formation processes, the cutting and polishing process, or general wear and tear over time. Pits are typically small and may require 10x magnification to be seen clearly, though larger pits can sometimes be visible to the naked eye.

When pits are larger and deeper, they are classified as cavities, which can have a more noticeable impact on a diamond’s clarity and durability. Pits and cavities are usually found on the table or facet junctions of a diamond, where they may affect the overall finish of the stone.

Pits can influence a diamond’s polish grade, as they interrupt the smoothness of the surface. While minor pits may not significantly impact a diamond’s appearance or value, excessive or deep pits can detract from its brilliance and make the stone more vulnerable to dirt accumulation or further damage.

In professional diamond grading reports from laboratories like the GIA or DCLA, pits are noted as part of the stone’s clarity characteristics. Jewelers and diamond cutters may attempt to minimize the visibility of pits through careful polishing, though in some cases, deep pits or cavities may require minor re-cutting to improve the diamond’s overall finish.

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Pink Diamond

A coloured diamond with a natural pink body colour. Pink must be the predominant colour, but it may be modified by shades of purple, orange, and yellow. The colour in natural pink diamonds is created by irregular crystal structure. Some pink coloured diamonds with sufficient saturation fall into the valuable fancy pink colour category of diamonds.

A pink diamond is a rare and highly sought-after coloured diamond that exhibits a natural pink body colour. To be classified as a pink diamond, pink must be the predominant hue, though it may be modified by secondary tones such as purple, orange, or yellow.

Unlike most coloured diamonds, which owe their hues to chemical impurities, the captivating colour of natural pink diamonds is attributed to distortions in their crystal lattice structure. These distortions, formed under immense pressure during the diamond’s geological formation, alter the way light interacts with the stone, producing its signature pink hue.

Pink diamonds vary in intensity, ranging from delicate pastel shades to deep, vivid pinks. Those with higher colour saturation are classified as Fancy Pink diamonds, a designation that significantly enhances their value. The most desirable pink diamonds display pure, strong pink tones with minimal secondary colours.

These exquisite gems are among the rarest diamonds in the world, with the finest specimens historically sourced from the Argyle mine in Australia, which ceased operations in 2020. The mine’s closure has further increased the rarity and value of high-quality pink diamonds. Today, they remain a prized choice for collectors and investors, often fetching record-breaking prices at auctions.

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Kimberlite

Kimberlite is an igneous rock, typically blue or green in colour, from which most diamonds are mined. It is of particular interest in the study of diamonds because it serves as the primary host rock for the formation and occurrence of these precious stones. Kimberlite is found in specific geological structures known as kimberlite pipes, which are deep, vertical fissures or conduits in the Earth’s crust. These pipes were formed by volcanic activity, and they are the main source of natural diamonds that are mined today.

Formation and Composition of Kimberlite
Kimberlite is an ultramafic rock, meaning it contains a high proportion of magnesium and iron, with low silica content. The primary components of kimberlite include:

Olivine: A green mineral that is a common constituent of kimberlite, contributing to its characteristic colour.
Pyroxenes: A group of minerals that also form part of kimberlite’s composition.
Carbonates: Minerals such as calcite and dolomite can be found in kimberlite, sometimes in large quantities.
Clay Minerals and Volcanic Ash: In some cases, kimberlite also contains elements derived from the surface, such as clay minerals or volcanic debris.
Diamond Crystals: Most notably, kimberlite contains diamonds, though the quantity and size of these diamonds vary.
The volcanic activity responsible for the formation of kimberlite pipes involves the eruption of magma from deep within the Earth’s mantle. This magma, under extremely high pressure and temperature, ascends through the Earth’s crust, bringing with it diamonds that formed under similar high-pressure conditions. Kimberlite, upon solidification, traps these diamonds within the rock, where they remain until mining operations bring them to the surface.

Kimberlite Pipes: The Primary Source of Diamonds
The most famous source of diamonds, kimberlite pipes, are vertical geological formations that originate from deep beneath the Earth’s surface. These pipes are often cylindrical in shape, and their formation is associated with ancient volcanic eruptions. As the magma ascends through the Earth’s crust, it forms a narrow, funnel-like conduit. Over millions of years, erosion and weathering can expose kimberlite pipes, allowing diamond mining to occur.

These pipes are typically surrounded by much older and harder rocks, often making it difficult to access the diamonds. The kimberlite itself can also contain other valuable minerals such as garnet, ilmenite, and chromite, but it is the diamonds embedded within the kimberlite that are the primary target of mining efforts.

The Role of Kimberlite in Diamond Mining
Kimberlite plays a crucial role in the discovery and extraction of diamonds. Mining operations often target kimberlite pipes, as they are the most reliable source of diamonds in nature. The process of mining kimberlite involves:

Exploration: Geologists and prospectors search for kimberlite pipes using various techniques such as aerial surveys, satellite imagery, and ground sampling. The distinctive blue or green colour of the rock can also be used as an indicator of its presence.

Extraction: Once a kimberlite pipe is located, it is typically extracted through either open-pit or underground mining techniques. Open-pit mining involves removing large quantities of surface material to reach the kimberlite layer, while underground mining involves digging shafts to reach deeper deposits.

Processing: After kimberlite is extracted, it is crushed and sorted to separate the diamonds from the surrounding rock and other minerals. This is typically done through a combination of mechanical crushing, gravity separation, and sometimes, advanced techniques such as X-ray sorting or dense media separation.

Geological and Geographic Distribution of Kimberlite
Kimberlite is found in specific geographic regions, primarily in ancient cratons—stable areas of the Earth’s crust that have remained relatively undisturbed for billions of years. These regions include:

Africa: The continent is home to several large kimberlite pipes, including the famous Kimberley Mine in South Africa, which has been historically significant for diamond mining.
Russia: Russia contains several diamond-producing kimberlite pipes, particularly in Siberia, with the Yakutia region being a major source of diamonds.
Canada: The discovery of kimberlite pipes in Canada’s Northwest Territories led to the establishment of large-scale diamond mining operations, such as the Ekati and Diavik mines.
Australia: The Argyle Mine in Western Australia, which produces significant quantities of pink and red diamonds, is also a notable source of kimberlite.
While kimberlite pipes are present on all continents, the largest and most significant diamond-producing regions are found in Africa, Russia, and Canada.

Importance and Rarity of Kimberlite Pipes
While kimberlite pipes are the main source of natural diamonds, they are relatively rare. The conditions required for kimberlite formation are very specific, and only a small number of these pipes have been discovered and mined for diamonds. Geologically speaking, kimberlite pipes are often formed in ancient and stable parts of the Earth’s crust, where volcanic activity can reach the depths necessary for diamond formation.

The rarity and difficulty of accessing kimberlite pipes make diamonds sourced from these pipes valuable commodities. The unique geological conditions under which kimberlite forms, combined with the rarity of pipes, contribute to the high value of diamonds that originate from these sources.

Kimberlite vs. Lamproite: Other Sources of Diamonds
While kimberlite is the most well-known source of diamonds, lamproite is another type of volcanic rock that can also host diamonds. Lamproite is less common than kimberlite, but some significant diamond deposits, such as those at the Argyle Mine in Australia, have been discovered in lamproite pipes. However, kimberlite remains the more prominent and studied source of diamonds worldwide.

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Gem Quality

Only about 20% of mined diamonds are of gem quality, meaning they meet the necessary standards for use in jewellery. The remaining 80% fall into the industrial-grade category, used in various commercial and technological applications. Let’s explore this in more detail:

Breakdown of Diamond Quality
Gem-Quality Diamonds (≈20%)

These diamonds are characterised by high clarity, colour, and cut quality, making them desirable for jewellery.
They undergo cutting and polishing to enhance their brilliance before being set in rings, necklaces, earrings, and other fine jewellery.
Their value depends on the 4 Cs (Carat, Cut, Colour, Clarity) and whether they are natural or treated.
Industrial-Grade Diamonds (≈80%)

These diamonds are lower in clarity, may have visible inclusions, and often exhibit yellow, brown, or grey colours that make them unsuitable for jewellery.
They are used in industries due to their hardness and durability, which are essential for cutting, drilling, grinding, and polishing applications.
Common uses include:
Diamond-tipped drill bits and saw blades for construction and mining.
Abrasive powders for polishing and grinding metals.
High-tech applications, such as semiconductors and heat conductors in electronics.
Why the Low Percentage of Gem-Quality Diamonds?
Several factors contribute to why only a small fraction of mined diamonds qualify as gem-grade:

Formation Conditions: Natural diamonds form under extreme pressure and temperature deep within the Earth’s mantle. Impurities or irregular growth can affect their clarity, colour, or shape.
Inclusions and Blemishes: Many diamonds contain internal inclusions (tiny fractures or foreign minerals) and external blemishes, making them less suitable for jewellery.
Colour and Transparency: Gem-quality diamonds are typically colourless to light yellow (D-Z on the GIA colour scale). Many mined diamonds have a strong brown or grey tint, reducing their desirability.
Cutting Yield: Some rough diamonds, even if of good quality, may be inefficiently shaped for cutting into marketable gemstones.
Impact on the Diamond Market
Rarity Drives Value: Since high-quality diamonds are less common, they retain their value better than industrial-grade diamonds.
Lab-Grown Diamonds: The gap in supply between industrial and gem-quality diamonds has led to advancements in lab-grown diamonds, which can be produced with high clarity and controlled quality.
Recycling & Recutting: Some lower-quality diamonds can be recut or treated (e.g., laser drilling, fracture filling) to enhance their appearance, but these diamonds are usually less valuable than untreated stones.

The fact that only 1 in 5 mined diamonds meets gem-quality standards highlights the rarity and value of fine diamonds. This also influences pricing, sourcing strategies, and market trends, as both natural and lab-grown diamonds compete in the luxury and industrial sectors.

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Coloured Diamond

Fancy-colour-Diamonds

A coloured diamond is a diamond that exhibits a hue other than the traditional colourless range. While most diamonds appear colourless or near-colourless, coloured diamonds come in a variety of shades, ranging from yellow, brown, and blue to rare colours like pink, green, and red. The colour in these diamonds is caused by elements or chemical processes during their formation, which result in various hues and saturations.

Key Types of Coloured Diamonds:
Yellow Diamonds:

Yellow diamonds are among the most common coloured diamonds and owe their hue to the presence of nitrogen atoms in the crystal lattice. The nitrogen atoms absorb blue light, resulting in the yellow colour.
These diamonds can range from light yellow to vibrant canary yellow.
Intensity and Saturation: The more intense the yellow colour, the more valuable the diamond. The colour is graded on a scale from light yellow to fancy vivid yellow.
Brown Diamonds:

Brown diamonds are also relatively common and are often referred to as chocolate diamonds or cognac diamonds based on their specific hue. The colour in brown diamonds is typically caused by plastic deformation during their formation, which results in the diamond absorbing blue light.
Brown diamonds can be found in various shades, including light brown, champagne, and rich cognac.
They are graded based on the depth of colour, with higher intensities like fancy intense brown being more valuable.
Blue Diamonds:

The striking blue colour of these diamonds is caused by the presence of boron atoms in the crystal lattice. Boron absorbs yellow and red light, leaving behind the blue hue.
Blue diamonds can range from light blue to vivid blue. The most famous blue diamond is the Hope Diamond, which is a deep blue.
The colour intensity plays a significant role in the value, with the more intense the blue, the more valuable the diamond.
Pink Diamonds:

Pink diamonds are some of the rarest and most sought-after coloured diamonds in the world. Their colour is thought to be the result of structural defects in the diamond’s crystal lattice, which causes the absorption of certain wavelengths of light.
The colour can range from light pink to vivid pink, with fancy intense pink diamonds being the most valuable.
Pink diamonds are primarily found in Australia’s Argyle mine, though the mine has since been closed, making these diamonds even rarer.
Green Diamonds:

Green diamonds derive their colour from the presence of natural radiation that causes the diamond to absorb certain wavelengths of light, leaving a greenish hue.
The green can range from light green to deep, vivid green. Natural green diamonds are quite rare and can be valuable depending on the intensity of the colour.
Treated green diamonds are also available, where the green hue is enhanced through a process known as irradiation.
Red Diamonds:

Red diamonds are among the rarest of all coloured diamonds, and their colour is often attributed to defects in the diamond’s crystal structure. The exact cause of the red colour is not fully understood, but it is believed to result from a particular defect that causes the diamond to absorb blue and yellow light.
The red diamond can range from light red to deep red, with the most famous example being the Moussaieff Red Diamond.
Due to their extreme rarity, red diamonds command extremely high prices.
Orange Diamonds:

Orange diamonds are rare and owe their colour to the presence of nitrogen atoms, similar to yellow diamonds. However, the arrangement of these nitrogen atoms results in a different colour spectrum.
These diamonds can range from light orange to deep fiery orange. The more intense the colour, the more valuable the diamond.
Purple Diamonds:

Purple diamonds are extremely rare and are often caused by a combination of structural defects and the presence of hydrogen during the diamond’s formation.
These diamonds typically show a mix of red and blue hues, which gives them a unique, vibrant appearance.
Colour Grading of Coloured Diamonds:
The grading system for coloured diamonds differs from that of colourless diamonds. Coloured diamonds are graded based on two main factors:

Hue: The colour of the diamond, such as yellow, blue, or pink.
Tone: The lightness or darkness of the colour (from light to dark).
Saturation: The intensity of the colour (from faint to vivid or intense).
Diamonds with more intense and saturated colours, especially those classified as fancy vivid, are typically the most valuable. Coloured diamonds are graded with terms like fancy light, fancy, fancy intense, and fancy vivid, where the more vivid the colour, the more valuable the diamond.

Factors Affecting the Value of Coloured Diamonds:
Rarity: The rarity of the colour is a major factor in determining the value of a coloured diamond. For example, red diamonds and blue diamonds are significantly rarer than yellow diamonds, making them more valuable.
Colour Intensity: The intensity of the colour (saturation and tone) greatly influences the price. Diamonds with vivid, deep hues command higher prices than those with lighter or less saturated colours.
Size: Coloured diamonds, like colourless diamonds, are valued by their carat weight. Larger coloured diamonds with strong, vivid colours are extremely rare and fetch exceptionally high prices.
Origin: Some coloured diamonds, like pink diamonds from the Argyle mine, are particularly valuable because of their rarity and the mine’s closure, making the diamonds even more scarce.
Treatments of Coloured Diamonds:
Some coloured diamonds undergo enhancement treatments to improve their colour. For example:

High Pressure High Temperature (HPHT) and irradiation are methods used to enhance the colour of diamonds, especially for those in the yellow, brown, and green ranges.
Natural coloured diamonds are often preferred for their uniqueness and value, as treated diamonds generally have a lower resale value.
The DCLA and Coloured Diamonds:
The DCLA (Diamond Certification Laboratory of Australia) offers colour grading for coloured diamonds using the standard grading scale and methodology, ensuring consistency with international grading systems. DCLA’s certification of coloured diamonds will include detailed colour information, including the hue, tone, and saturation of the diamond, providing buyers with a comprehensive understanding of the diamond’s quality and characteristics.

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Annealing

artificially enhance the colour of a diamond

Annealing diamond refers to a process in which diamonds are heated to high temperatures in a controlled environment to alter their internal structure or appearance. However, diamond annealing is quite different from annealing in other materials, like metals, because diamonds are already a highly stable, hard material. The process is typically used to modify certain properties of the diamond, such as colour or internal inclusions, rather than improving the material’s hardness or strength.

Here are the key aspects of diamond annealing:

1. Annealing to Alter Colour:
Annealing can be used to change or enhance the colour of a diamond. This is often done to lighten or darken the stone’s hue, or to bring out more desirable tones, like in fancy colour diamonds.

Heating Process: The diamond is subjected to high temperatures (sometimes exceeding 1000°C) in a controlled environment, typically in a vacuum or in an atmosphere of certain gases, such as nitrogen or hydrogen.
Effect on Colour: The heat causes changes in the diamond’s crystal structure, which can alter how light interacts with the stone, thus changing its colour. For instance, diamonds with brownish hues may turn to a lighter yellow or even white, while others might enhance their natural colour intensity.
2. Healing Inclusions (Internal Cracks or Imperfections):
Another purpose of annealing is to reduce the visibility of certain inclusions, particularly graining or small cracks. In this case, annealing can:

Relieve Stress: The heat from annealing can relieve internal stress in the diamond, causing cracks or inclusions to become less visible. This is especially useful for diamonds that have inclusions located near the surface, which can affect the diamond’s clarity.
Mend Cracks: Under controlled conditions, the annealing process can sometimes cause minor surface fractures to heal by encouraging the material around the crack to bond back together.
3. Limitations and Risks:
High Temperature: Because diamonds are made of carbon in a crystal lattice structure, they can be sensitive to extreme heat. The temperature and environment must be carefully controlled during the annealing process to prevent damaging the stone. If not done properly, excessive heat can cause the diamond to fracture or even shatter.
Not Suitable for All Diamonds: Annealing is not always suitable for all diamonds. For instance, diamonds with a high degree of internal stress or fractures may not respond well to heat treatment, as the process could cause further damage.
4. Impact on Diamond Value:
Colour Alteration: If annealing is used to improve the colour of a diamond, it can enhance the stone’s appearance and potentially increase its value, especially for diamonds with rare or sought-after colours.
Clarity Improvement: If annealing successfully reduces the visibility of inclusions, it can improve the diamond’s clarity, which could also make the diamond more valuable. However, some buyers may be cautious about diamonds that have undergone treatment, as they may prefer natural diamonds without any enhancements.
Disclosure: When diamonds are annealed or treated in any way, it’s important for sellers to disclose the treatment. Some buyers prefer untreated, natural diamonds, and the presence of treatment may affect the resale value or marketability.
5. Annealing in Industry:
While annealing is a term more commonly associated with metals or other materials, it is sometimes used in the diamond industry for specific treatments to improve the visual appeal or structural integrity of the diamond. The process is not typically used to improve hardness—since diamonds are already the hardest known material—but rather to address aesthetic and internal concerns.

Summary:
Annealing diamond involves heating the diamond to high temperatures in a controlled environment to alter its colour or reduce the visibility of internal inclusions.
It is often used to enhance the colour or improve the clarity of diamonds.
The process requires careful control to avoid damaging the diamond.
Annealed diamonds should be disclosed as treated, as they may affect the value, depending on the buyer’s preferences.

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If I buy a certified diamond, how do I know that the diamond in my ring is the one described on the diamond certificate or diamond grading report?

There are a number of ways to verify that your diamond matches the diamond certificate it is purchased with. If you purchased a diamond that is laser inscribed, ask your jeweller to show you the laser inscription under magnification. This way, you will always be able to identify the diamond as your own.

DCLA also performs a verification service, for both DCLA certified diamonds and for diamonds certified by other internationally recognised laboratories. Bring  or send your diamond, together with the diamond grading certificate, to the DCLA laboratory and the diamond will be conclusively matched against the certificate. DCLA can then cold laser inscribe the diamond with either the diamond grading certificate number, or with a personalised message.

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How do I know that my diamond certificate or diamond grading report is from an independent laboratory ?

Ask the jeweller if the diamond certificate comes from an independent diamond laboratory or if it produced by a diamond merchant or retailer, then do your research. Make sure the certificate is issued by the DCLA or another highly respected diamond grading laboratory; DCLA is the only diamond grading laboratory worldwide to offer a full-replacement Diamond Grading Guarantee.

Lucara Sells Its 813 Carat Diamond for US$63 Million

Lucara Sells Its 813 Carat Diamond for US$63 Million, the Highest Price Ever Achieved for the Sale of a Rough Diamond.
Lucara Sells Its 813 Carat Diamond for US$63 Million, the Highest Price Ever Achieved for the Sale of a Rough Diamond.

Lucara Sells Its 813 Carat Diamond for US$63 Million, the Highest Price Ever Achieved for the Sale of a Rough Diamond.

Lucara, is pleased to announce that the exceptional 812.77 carat, Type IIa diamond recovered from the Karowe mine in Botswana in November 2015, has been sold for US$63,111,111 (US$77,649 per carat).

As part of the sale, Lucara has partnered with Nemesis International DMCC, and retains a 10% interest in the net profit received from the sale of the resultant polished diamonds.

The 813 carat diamond has been named, “The Constellation”, in collaboration with our partner. Lucara is a well-positioned diamond producer.

The Company’s main producing asset is the 100% owned Karowe Mine in Botswana.