Diamonds – Page 58 – The Diamond Certification Laboratory of Australia (DCLA)

July, 2017February, 2025

Upper-Girdle Facet

An Upper-Girdle Facet refers to a triangle-shaped facet that is positioned along the girdle of a diamond, specifically on the crown portion. These facets are part of the overall diamond structure and play a role in both the aesthetic appeal and the light performance of the diamond. They are located just above the girdle (the widest part of the diamond), and they help to define the outline and symmetry of the diamond.

Key Characteristics of Upper-Girdle Facets
Location:

The upper-girdle facets are found on the crown of the diamond, which is the top portion above the girdle. The facets extend from the girdle towards the top of the diamond, near the table facet.
These facets are positioned between the star facets (which surround the table) and the bezel facets (which form the uppermost portion of the crown, adjacent to the girdle).
Shape:

The upper-girdle facets are typically triangle-shaped, although their exact shape can vary slightly depending on the cut of the diamond.
The facet shape is designed to complement the overall geometry of the diamond and align symmetrically with the other facets to ensure optimal light reflection and brilliance.
Function and Impact:

Upper-girdle facets play an important role in the light performance of a diamond. They help to create the overall brilliance and scintillation (the flashes of light) seen when the diamond is moved.
These facets aid in directing light into the diamond and back out through the top, contributing to the sparkle and life that diamonds are known for. The way these facets are cut affects how well light enters the diamond, as well as how it is reflected and dispersed, enhancing the fire and brilliance.
Proportions and Symmetry:

Upper-girdle facets are often assessed in terms of proportions and symmetry during diamond grading. When properly aligned and proportioned, they contribute positively to the overall visual appeal of the diamond.
These facets need to be carefully crafted to ensure that they work in harmony with the other facets, such as the table, bezel facets, and pavilion facets, to produce the maximum amount of light reflection and refraction.
Importance in Diamond Cut:

Upper-girdle facets are part of the overall cut quality of the diamond, which is one of the most important factors in determining its value and visual appeal.
The quality of the cut—including how the upper-girdle facets are shaped, sized, and aligned—directly affects the diamond’s brilliance and scintillation. Therefore, these facets are essential in achieving an excellent cut grade on a diamond grading report.
Role in Different Cuts
In the most popular diamond shape, the round brilliant cut, the upper-girdle facets are specifically designed to enhance the diamond’s ability to reflect light and produce the desired sparkle.
In fancy-shaped diamonds, such as emerald cut or pear-shaped diamonds, the use of upper-girdle facets may vary or be absent, as different cutting styles have different faceting structures tailored to the shape and proportions of the diamond.
Visual and Aesthetic Impact
Properly cut upper-girdle facets contribute to the diamond’s symmetry and overall visual appeal. When these facets are aligned and proportioned correctly, they create a diamond that has a balanced, harmonious appearance.
These facets can also affect the appearance of the diamond’s size, as they help to define the outer edges of the diamond, creating the appearance of a larger, more well-defined shape.

The upper-girdle facets of a diamond are important, triangular facets positioned on the crown just above the girdle. These facets play a significant role in the diamond’s light performance, contributing to its brilliance, fire, and overall aesthetic appeal. The alignment and proportion of upper-girdle facets are crucial for ensuring a well-cut diamond that exhibits maximum sparkle. Their position and shape help to enhance the overall symmetry and light reflection, making them an essential element in the overall cut quality and beauty of the diamond.

July, 2017February, 2025

Wavy Girdle

A wavy girdle refers to a girdle of a diamond that is uneven in thickness or does not maintain a consistent, smooth plane all the way around the diamond’s circumference. This type of girdle is irregular, and rather than being perfectly straight and uniform, it undulates, creating a wave-like pattern along the edge of the diamond.

Key Characteristics of a Wavy Girdle
Uneven Thickness:

In a wavy girdle, the thickness of the girdle is not uniform. Some sections may be slightly thicker, while others are thinner. This unevenness in thickness can create a noticeable waviness around the diamond’s edge.
The girdle is the outermost edge of the diamond, and its thickness is important in protecting the stone from chips and fractures. A wavy girdle may make the diamond more prone to damage in certain areas due to its inconsistency.
Shape and Appearance:

A wavy girdle does not follow a straight, flat plane around the diamond. Instead, it may have a more undulating, curving, or irregular appearance. This undulation can result from imperfections in the rough diamond or the cutting process.
The effect is not always visible to the naked eye but can be detected under magnification or with careful inspection, especially if the waves are pronounced.
Effect on Symmetry:

The symmetry of a diamond is a critical aspect of its overall cut grade. A wavy girdle negatively impacts the symmetry of the diamond, as it deviates from the ideal, uniform shape that is expected from a well-cut diamond.
Since symmetry is a significant factor in the visual appeal of a diamond, a wavy girdle can detract from the diamond’s overall aesthetic and brilliance. It may cause slight misalignment in the overall shape of the diamond, making it appear less polished or balanced.
Impact on Diamond Grading:

When grading a diamond, the symmetry and girdle quality are evaluated. A wavy girdle will typically result in a lower symmetry grade. The grading report will often reflect this flaw, which can affect the overall value of the diamond.
A diamond with a wavy girdle may receive a grade that indicates some loss of symmetry, which can influence its desirability for certain buyers.
Causes of a Wavy Girdle:

A wavy girdle can result from the natural formation of the diamond in the earth or from imperfections in the cutting process. When the diamond is being cut, a lack of precision or inconsistency in the cutting machinery can lead to uneven girdle contours.
The shape of the original rough diamond may also play a role in the creation of a wavy girdle. In some cases, rough diamonds may have natural cracks, inclusions, or irregularities that cause the girdle to be cut unevenly.
Potential for Damage:

While the girdle is designed to protect the diamond from damage, a wavy girdle can sometimes create weak points or areas that are more vulnerable to chipping or cracking. Since the thickness varies along the edge, certain areas of the girdle may be thinner, making those points more prone to injury.
Aesthetic Impact:

Although a wavy girdle may not be immediately noticeable, it can impact the overall shape of the diamond, especially in certain cuts. For instance, in round brilliant or princess cuts, where symmetry is key, a wavy girdle may disrupt the round or square shape, creating an unbalanced or slightly skewed appearance.
For diamonds with specific shapes, such as emerald or pear-shaped, a wavy girdle can alter the uniformity of the outline, which may detract from the symmetry and elegance of the stone.

A wavy girdle is an irregularity in the girdle of a diamond, where the thickness varies or the edge does not follow a consistent plane. This can result from natural imperfections in the rough diamond or the cutting process and can negatively affect the symmetry and overall appearance of the diamond. A wavy girdle typically leads to a lower symmetry grade during the grading process, which in turn may impact the diamond’s value and desirability. Although it may not be immediately visible, a wavy girdle can influence the aesthetic balance and light performance of the diamond, making it an important factor to consider in a diamond’s evaluation.

July, 2017February, 2025

Trilliant

Diamond cut or shaped into a triangle, sometimes with curved sides.

A Trilliant cut, also known as a trillion cut, is a diamond shape characterised by its triangle-like outline. This cut is typically symmetrical, with three sides and sharp, pointed corners. The sides of the Trilliant cut may be straight or, in some cases, slightly curved, giving the shape a more rounded appearance depending on the specific design.

This diamond shape is distinctive for its triangular form, and it can be cut in varying styles, from classic triangles with straight edges to more softened versions where the sides are slightly curved. While the Trilliant cut can be used for both round and square diamonds, it is most commonly associated with fancy shape diamonds, offering a modern alternative to traditional shapes like the round brilliant or the pear cut.

Trilliant Cut Characteristics
Shape:

The Trilliant cut has a triangular shape with sharp corners. The edges can be either straight or slightly curved, depending on the design. The curved edges are sometimes referred to as the “modified” Trilliant cut, offering a softer, more rounded appearance.
Facets:

Typically, a Trilliant cut diamond features fewer facets than more intricate cuts like the round brilliant, but it often includes kite-shaped facets on the crown and pavilion. The number of facets can vary, but most Trilliant cuts have around 41 facets in total. The way the facets are arranged plays a significant role in the diamond’s brilliance and sparkle.
Symmetry and Proportions:

Like other diamond cuts, the symmetry of the Trilliant cut is important for ensuring it achieves the best possible brilliance and sparkle. The proportions, including the depth, table size, and crown angle, are critical to its performance in light reflection and dispersion.
Versatility:

The Trilliant cut is highly versatile and can be used for both solitaires and accent stones in a variety of jewellery pieces, including engagement rings, earrings, necklaces, and bracelets. It can be a striking centrepiece or serve as a complementary stone alongside other diamond shapes, adding a bold and contemporary touch.
Variations:

The traditional Trilliant cut is a right-angle triangle, with equal sides. However, variations include elongated Trilliant diamonds, which have more rectangular-like proportions, and curved-edge Trilliant diamonds, which offer a softer and more organic look.
Appeal and Advantages of the Trilliant Cut
Unique Appearance:

One of the primary draws of the Trilliant cut is its distinctive and contemporary look. The clean lines and sharp angles create a bold, dramatic effect that stands out compared to more traditional diamond shapes.
Brilliance and Fire:

The brilliance of a Trilliant cut diamond depends heavily on its proportions and the quality of the cut. Although it has fewer facets than the round brilliant cut, a well-proportioned Trilliant diamond can still exhibit significant brilliance and fire, with flashes of colour and light as the diamond is moved.
Versatile Settings:

Trilliant diamonds can be set in a variety of metal settings, including platinum, white gold, yellow gold, or rose gold, which allow the unique shape to shine in any type of design. Their triangular shape pairs well with both modern and vintage-inspired jewellery settings.
Good Use of Size:

Due to the nature of the Trilliant cut, this shape can help maximise the visual size of smaller diamonds. Because the shape is relatively compact compared to some other fancy cuts, it gives the appearance of a larger diamond while maintaining a well-balanced appearance.
Ideal Uses for Trilliant Cut Diamonds
Engagement Rings:

While the round brilliant cut remains the most popular choice for engagement rings, the Trilliant cut offers a unique alternative for those looking for something different. It can be used as a centre stone or as accent stones around a larger central diamond to create a dramatic effect.
Accent Stones:

The Trilliant cut is often used as an accent stone in designs, particularly alongside round diamonds or emerald cuts. The triangular shape can provide contrast and create a striking focal point in jewellery pieces such as rings, earrings, and pendants.
Modern Jewellery Designs:

Its angular, contemporary look makes the Trilliant cut particularly suited for modern and bold jewellery designs. Whether paired with white diamonds, coloured gemstones, or used alone, the Trilliant cut adds a striking and edgy element to any piece.
Considerations and Drawbacks
Visibility of Inclusions:

Like many fancy cuts, the Trilliant cut’s open design can sometimes make inclusions more visible than they would be in other cuts. This is particularly true for diamonds with lower clarity grades, so it’s important to choose a high-quality diamond for this cut to ensure it is eye-clean.
Size Perception:

While the Trilliant cut is often used for its distinctive appearance, its compact shape may make a diamond appear smaller than a similarly carat-weighted round diamond. For those prioritising size, it is essential to consider the proportions and angles of the cut.

The Trilliant cut is a bold and eye-catching diamond shape that offers a unique alternative to traditional round diamonds. With its triangular form and sharp corners, this cut is ideal for those looking for a contemporary, statement-making diamond. Whether used as a central stone or as part of a design with accent diamonds, the Trilliant cut can add brilliance, fire, and a touch of modern elegance to any jewellery piece.

July, 2017February, 2025

Twinning Line

A Twinning Line is a specific type of diamond inclusion that appears as a line or ribbon of small marks, which can include pinpoints, feathers, clouds, and crystals. These lines are typically visible under magnification and are a result of the natural growth process of diamonds within the Earth’s crust. They are a characteristic feature of diamonds that have undergone the complex geological conditions that contribute to their formation.

Formation of Twinning Lines
Twinning lines are created when two rough diamonds have grown together during the process of diamond formation, which takes place deep within the Earth under extreme heat and pressure. This interaction causes a part of the diamond’s crystal structure to form in alignment with the other diamond, resulting in the characteristic lines or ribbons of inclusions.

In most cases, the twinning line represents the point where two diamond crystals have joined or interacted during the diamond’s formation. Over time, as the diamonds are subjected to various geological pressures and environmental conditions, these areas of growth can lead to the inclusion of tiny pinpoints, feathers, or other microscopic crystals, creating a visible line within the diamond’s structure.

Characteristics of Twinning Lines
Appearance:

Twinning lines appear as linear inclusions that may be faint or more prominent depending on the diamond. The line often looks like a ribbon or strip, and it may be composed of multiple inclusions, such as pinpoints, tiny feathers, or clouds, which are all clustered together in the line.
These lines can vary in appearance, some being thin and subtle, while others may be more bold and visible under magnification.
Location:

Twinning lines are typically found within the interior of the diamond, often extending across the girdle, pavilion, or crown. However, the location can vary, and they may be visible on any facet of the diamond, depending on how the rough diamond has formed.
The inclusions formed by twinning lines may not always be visible to the naked eye, but they are often detectable under 10x magnification, which is commonly used by gemologists to inspect diamonds during grading.
Nature of Inclusions:

The inclusions that form along twinning lines are often a mix of pinpoints (tiny, round inclusions), feathers (thin, hair-like cracks or fractures), clouds (groupings of pinpoints or other inclusions that create a hazy appearance), and crystals (other mineral crystals that may be trapped inside the diamond).
These inclusions are usually microscopic, but in some cases, they can affect the overall clarity of the diamond, depending on their size and concentration.
Gemological Significance of Twinning Lines
Identification:

Twinning lines serve as an important feature for identifying diamonds. They are a unique inclusion type that is generally found in natural diamonds, making them a useful tool for gemologists and diamond appraisers when distinguishing between natural and synthetic diamonds.
When present, twinning lines are often recorded in the diamond’s grading report to help trace the diamond’s origins and confirm its authenticity.
Clarity Grade Impact:

The presence of twinning lines can affect the clarity grade of a diamond. Depending on the visibility and size of the inclusions within the twinning line, they may cause the diamond to be graded lower for clarity. However, if the twinning line is internal and does not interfere with the diamond’s surface or overall aesthetic appeal, the impact on the clarity grade may be minimal.
In some cases, diamonds with visible twinning lines might be priced lower than those with fewer or no inclusions, though this also depends on other factors such as the diamond’s size, cut, and colour.
Value Consideration:

Twinning lines do not necessarily have a significant effect on a diamond’s overall market value, particularly if they are small and not easily visible to the naked eye. However, in diamonds with heavier twinning inclusions, these markings may slightly decrease the value depending on their visibility and impact on the diamond’s overall appearance and clarity.
For many diamond buyers, the presence of twinning lines might not be a major concern, especially when purchasing diamonds with high colour and cut quality. However, collectors or those seeking the most flawless diamonds may prefer stones that are free from such inclusions.
Twinning Lines and Diamond Quality
Impact on Aesthetics:

Twinning lines are generally considered natural features of a diamond and are not seen as negative traits by many buyers. While they may cause slight cloudiness or haziness, particularly when accompanied by other inclusions, they do not detract from the overall beauty of the diamond as long as they are not too prominent.
The quality of the diamond’s cut can sometimes mitigate the effects of twinning lines, as a well-cut diamond will often have more sparkle and brilliance, making inclusions like twinning lines less noticeable.
The “Twinning” Phenomenon:

The term “twinning” refers to a specific crystallographic phenomenon where the crystal lattice of two diamond crystals becomes intertwined during their formation. This causes the diamonds to grow in mirror-image symmetry, leading to the creation of the twinning line. This natural occurrence can make diamonds with twinning lines unique and interesting, offering a fascinating glimpse into the diamond’s formation process.

Twinning lines are an intriguing and distinctive type of diamond inclusion formed when two rough diamonds grow together during the natural crystallisation process. These lines appear as ribbons or stripes of small inclusions, such as pinpoints, feathers, clouds, and crystals. While they can affect the diamond’s clarity grade, they are typically a natural characteristic and are often used by gemologists to authenticate diamonds. The presence of twinning lines can slightly decrease a diamond’s value, but they do not necessarily detract from the diamond’s overall beauty or brilliance, especially if they are small and not easily visible to the naked eye.

July, 2017February, 2025

Treated Diamond

A treated diamond refers to a diamond that has undergone artificial enhancement to improve one or more of its natural characteristics, typically either its colour or clarity. These treatments can significantly alter the appearance of the diamond from its original state, and they may influence its value and marketability. As a result, any treatment a diamond has undergone must be fully disclosed to ensure transparency in the diamond’s history and characteristics.

Diamonds that are treated are usually more affordable than untreated diamonds with similar characteristics because the treatments aim to improve attributes such as colour intensity or the visibility of inclusions. However, treated diamonds are often valued less than their natural, untreated counterparts due to the fact that they do not retain the same rarity or intrinsic value.

Types of Diamond Treatments
Laser Drilling:

Laser drilling is a process used to reduce the visibility of inclusions, especially those near the surface of the diamond. A laser is used to create a small hole into the diamond, which is then filled with a material such as glass or resin to make the inclusion less noticeable.
While laser drilling can improve the clarity of a diamond, it leaves behind tiny, microscopic marks that are visible under magnification. These marks should be disclosed on a grading report.
High-Temperature, High-Pressure (HTHP) Treatment:

The HTHP method is used primarily to improve the colour of diamonds, especially those with a lower colour grade (yellow or brown diamonds). This treatment involves subjecting the diamond to high temperatures and pressures, simulating the conditions under which diamonds form in the earth.
HTHP treatment can also be used to enhance the natural blue or green colour of diamonds. However, it can cause some diamonds to change colour in ways that are not predictable, and the effects of the treatment can sometimes fade over time.
Laser Ablation:

Laser ablation is a process used to remove or reduce the appearance of inclusions and blemishes in a diamond. In this treatment, lasers are used to burn away the inclusions, leaving behind a clearer stone.
This process is more precise than laser drilling and can be used to remove darker inclusions, making the diamond appear cleaner. However, like laser drilling, it leaves small marks that can be detected under magnification.
Clarity Enhancement:

Clarity enhancement includes methods like laser drilling and fracture filling (where fractures in the diamond are filled with a special resin to make them less visible). These treatments aim to improve the diamond’s clarity grade by reducing the visibility of inclusions or fractures.
Clarity enhancements can have a lasting effect on the diamond’s appearance, but the treatments may also affect the diamond’s durability over time, especially in the case of fracture filling.
Fracture Filling:

Fracture filling is a treatment designed to improve the clarity of diamonds with visible cracks or fractures. A special filling material is injected into the diamond’s surface cracks, which makes the fractures less noticeable.
The filling material used in this process can sometimes wear away or discolor over time, especially if exposed to heat or certain chemicals. This makes fracture-filled diamonds potentially less durable in the long term.
Ion Implantation:

Ion implantation is a technique used to modify a diamond’s colour by implanting small amounts of specific elements, such as nitrogen or boron, into the diamond’s surface. This can change the diamond’s hue to a desired shade, often enhancing or altering the diamond’s overall colour.
While this method can create vibrant colours, the resulting diamond may not be as durable as untreated diamonds because the process only affects the surface layer, leaving the rest of the diamond in its natural state.
Coating:

Some diamonds are treated with a coating to improve their appearance. These coatings can enhance the colour, giving the diamond a more intense hue, or improve the clarity by hiding inclusions. Common coatings include diamond-like carbon (DLC) or enhancement coatings.
Coatings are often temporary and can wear off over time, especially if the diamond is exposed to harsh conditions such as abrasion, heat, or chemicals.
Colour Enhancement:

This treatment is primarily used on diamonds that are near the lower end of the colour scale, often brown or yellow diamonds. Using various techniques, including the HTHP method, lasers, or irradiation, the natural colour of the diamond can be enhanced to give it a more vibrant and desirable hue.
Colour-enhanced diamonds are often referred to as “fancy colour diamonds” if they fall into specific ranges of colour intensity and saturation, such as blue, green, or pink. However, the enhancement process must be disclosed, as it can impact the overall value and authenticity of the diamond.
Irradiation:

Irradiation involves exposing diamonds to radiation to alter their colour, often producing intense blues, greens, or other rare colours. The treatment can also be combined with the HTHP process to deepen the colour of diamonds.
Irradiation treatments can result in a permanent change to the diamond’s colour, but these diamonds are still considered treated diamonds and should be evaluated for their overall condition and authenticity.
Disclosure of Treated Diamonds
Because treated diamonds have undergone artificial enhancement, their treatments must be disclosed when they are bought, sold, or traded. Failure to disclose a diamond’s treatment status can be considered fraudulent and may lead to legal consequences. It is crucial for consumers and dealers to understand that while treated diamonds may offer a more affordable option, they typically hold a lower value than natural, untreated diamonds due to the fact that their characteristics have been artificially altered.

Market Considerations and Value
The value of a treated diamond is typically lower than that of a natural, untreated diamond with similar appearance and specifications. This is because treated diamonds are considered less rare and may not have the same long-term durability. Additionally, the resale value of treated diamonds is often lower due to the artificial nature of the enhancements.

Fancy Colour Treated Diamonds are an exception in some cases, where treated diamonds with vibrant, rare colours such as blue or green may still command a premium, especially if the colour enhancement is carefully controlled and results in a highly sought-after hue.

Treated diamonds have been artificially altered to improve their colour or clarity, making them more affordable and attractive to some buyers. However, the treatments can affect their long-term durability and value, so it is crucial for both buyers and sellers to fully disclose any treatments performed on a diamond. Transparency in the market helps to maintain trust and allows customers to make informed decisions when purchasing diamonds.

July, 2017February, 2025

Trigon

A Trigon is a unique feature found in some natural diamonds that is characterised by its triangular shape, often appearing as fine, concentric triangular lines or marks. These trigon patterns are typically seen on the surface of the diamond, and they form due to the natural growth and crystal structure of the diamond during its formation deep within the Earth.

Trigons are particularly important in the field of diamond identification and diamond grading, as their presence can serve as a definitive indicator that a diamond is natural, distinguishing it from synthetic or man-made diamonds. These markings are not commonly found on diamonds that have been synthetically produced in a laboratory environment, making them a key feature for gemologists when verifying the authenticity of a diamond.

Formation of Trigons
Trigons are formed as part of the natural crystallisation process of a diamond. They arise from the growth patterns within the diamond’s crystal lattice. As the diamond forms under extreme heat and pressure deep within the Earth, the atoms in the crystal align in a very specific way, leading to the appearance of these fine triangular lines on the surface of the diamond.

The exact appearance and positioning of the trigons can vary depending on the specific growth conditions and the orientation of the diamond’s crystal structure. While the trigons themselves may be very fine and microscopic, they are typically visible under magnification using tools like a jeweller’s loupe or microscope.

Identification of Natural Diamonds
Trigons are a strong indicator that a diamond is natural, as they are rarely, if ever, seen in synthetic diamonds. The formation of these fine triangular lines is a direct result of the natural growth process of diamonds, and their presence can be considered one of the tell-tale features used by gemologists to confirm a diamond’s authenticity.

When a diamond is subjected to high magnification, these trigons are typically seen as small, triangular grooves or lines that radiate from the centre of the facet, resembling a fan-like or concentric pattern. They are often most visible on the pavilion facets of the diamond, though they can occasionally be found on the crown facets as well.

Trigon Markings and Natural Diamond Identification
Because trigons are exclusive to natural diamonds, they play a vital role in the gemological analysis of diamonds. Advanced testing and examination techniques, such as microscopic examination or spectroscopic analysis, can reveal these markings, providing a clear distinction between natural and synthetic diamonds.

Furthermore, Trigons are particularly significant for diamond authentication. In addition to other characteristics, such as inclusions or crystal formation patterns, trigons offer a way for gemologists to trace a diamond’s origin and determine whether it has been subject to artificial creation processes.

Importance in the Diamond Market
While trigons are a natural feature, their presence can sometimes add to the uniqueness of a diamond, particularly in the context of natural diamond collections and antique jewellery. For collectors or buyers of natural diamonds, the presence of trigons may enhance the perceived value, as it adds a layer of authenticity and rarity to the gemstone.

In addition, these natural growth features can be a useful tool for diamond appraisers and gemologists who are tasked with identifying and grading diamonds. Trigons help confirm that the diamond has not been altered, treated, or synthetically produced, ensuring that it maintains its full natural value.

Trigons are triangular, concentric marks found in natural diamonds, created by the crystal growth process deep within the Earth. These fine markings are a definitive indicator of a diamond’s natural origin and are used by gemologists and appraisers to authenticate diamonds. Trigons are an important feature in distinguishing natural diamonds from synthetic diamonds, and their presence contributes to the unique nature of a natural diamond.

July, 2017February, 2025

Toughness

$Toughness Measure of brittleness, or resistance to fracture and breaking$

Toughness refers to a diamond’s resistance to fracture or breaking when subjected to impact or stress. While diamonds are known for their exceptional hardness, which allows them to resist scratching and abrasion, toughness measures how well a diamond can withstand physical force, such as chipping or cracking. Toughness is an essential characteristic when evaluating the durability of a diamond, particularly when it comes to everyday wear and usage in jewellery.

Though diamonds are one of the hardest materials on Earth, they are not immune to damage. Due to the crystal structure of diamonds, they have certain planes of weakness that can make them susceptible to breaking if impacted along these planes. Therefore, while a diamond may not scratch easily, it can still fracture or split under the right conditions. This makes toughness an important factor in assessing how a diamond will perform in real-world scenarios, such as in rings or other jewellery that is regularly exposed to physical stress.

Understanding Diamond Toughness:
Hardness vs. Toughness:

Hardness refers to a material’s ability to resist scratching, and diamonds are the hardest known natural substance, scoring a 10 on the Mohs scale of hardness.
Toughness, on the other hand, refers to how well a material can absorb energy without breaking or fracturing. While diamonds are incredibly hard, they are not as tough as some other materials due to their brittleness. This means that while diamonds can resist scratching, they may be more prone to chipping or cracking if hit at certain angles.
Directional Hardness:

One of the key factors influencing the toughness of a diamond is its directional hardness. Diamonds have a crystal structure known as cubic or isometric, which means that their atoms are arranged in a specific way that makes them incredibly hard in certain directions but more vulnerable in others.
While the diamond is extremely hard along its axes, this structural alignment can make it more prone to cleaving or splitting along certain planes, especially when it experiences a strong impact. These planes of weakness make diamonds more fragile in some situations, particularly if subjected to sharp blows or pressure.
Toughness Rating:

Diamonds do not have a standard toughness rating in the same way that they are graded for hardness. However, toughness is typically described in terms of how resistant a diamond is to breaking, chipping, or fracturing.
Toughness can be affected by factors such as the quality of the cut, inclusions, and fractures present in the diamond. A diamond with significant internal flaws, such as inclusions, may be less tough and more likely to break or chip under stress than a flawless diamond.
Factors Influencing Diamond Toughness:

Clarity: Diamonds with inclusions or internal fractures are generally more prone to breakage. These internal weaknesses can compromise the diamond’s toughness, making it more vulnerable to impact.
Cut Quality: A well-cut diamond with proper proportions and symmetry will often be more durable, as the cut will reduce the likelihood of creating stress points where fractures could occur. A poorly cut diamond may have internal tensions that make it more fragile.
Size and Shape: Larger diamonds or diamonds with more complex shapes (like those with sharp corners or thin edges) may be more susceptible to chipping or fracturing if impacted. The shape and overall structure of the diamond can affect its ability to absorb force without damage.
Real-World Application:

While diamonds are the hardest known material, their brittleness means that they need to be handled with care. Diamonds used in jewellery, such as engagement rings or bracelets, are typically designed to avoid exposure to significant impact or stress.
For example, diamonds with sharp corners (like princess cut diamonds) or thin edges (like emerald cut diamonds) may be more susceptible to chipping than those with rounder shapes, such as the round brilliant cut, which typically has a stronger overall structure.
Bezel settings or halo settings in jewellery can offer additional protection to the diamond, keeping it shielded from accidental impact.
Toughness in Coloured Diamonds:

While most of the principles regarding diamond toughness apply to colourless diamonds, coloured diamonds may have their own unique challenges. For example, some coloured diamonds, especially those with intense colours like red or blue, may have inclusions or internal characteristics that affect their toughness.
Coloured diamonds, due to their often unique internal structures, may exhibit slightly different behaviour under impact, but they still share the same basic brittleness as other diamonds.
Toughness and Diamond Jewellery:

When choosing a diamond for daily wear jewellery, toughness is an important consideration, especially for items like engagement rings, which are subject to constant wear and potential impact.
A diamond’s setting also plays a role in how well it can withstand rough treatment. A prong setting, for example, may expose the diamond to more risk of damage, while a bezel setting can offer more protection.

Diamond toughness is an essential characteristic that determines a diamond’s ability to withstand impact and stress without fracturing or breaking. Although diamonds are the hardest material on Earth, their brittleness means they can still break along planes of weakness in their crystal structure. Therefore, toughness is closely linked to hardness but involves how well a diamond resists fractures, chips, and cracks from physical force. When choosing a diamond for jewellery, it is important to consider the diamond’s clarity, cut, and shape, as these factors can influence the diamond’s overall toughness and resistance to damage.

July, 2017February, 2025

Table

The table is one of the most important facets of a polished diamond, situated at the very top of the diamond, in the crown area. It is the largest flat facet on the diamond and plays a crucial role in how light interacts with the stone. The table facet is typically positioned parallel to the girdle, which is the outermost edge of the diamond, and it serves as a window through which light enters and exits the diamond. The size and proportion of the table facet significantly impact the overall appearance, brilliance, and sparkle of the diamond.

Position and Shape:
The table is flat and circular in shape, with its size and dimensions typically defined as a percentage of the diameter of the diamond, measured from the girdle.
It is placed directly at the top of the diamond, centered on the crown. For round brilliant cut diamonds, the table should be symmetrical to allow for even light reflection and maximum brilliance.
The size of the table relative to the overall dimensions of the diamond is an important factor in its overall cut quality and light performance. A table that is too large or too small can negatively affect the diamond’s visual appeal.
Role of the Table in Diamond Brilliance:
The table facet is the primary surface through which light enters the diamond, and its quality directly influences the diamond’s brilliance (the amount of white light reflected). Light entering the table facet is refracted through the diamond’s other facets, creating the sparkle and life that is characteristic of a well-cut diamond.
If the table is too large, it may result in excessive light leakage, where light passes through the bottom of the diamond, reducing its brilliance. Conversely, a table that is too small may limit the diamond’s ability to reflect light effectively, making the diamond appear darker or less vibrant.
Table and Diamond Cut Quality:
The size of the table is one of the key factors considered when assessing a diamond’s cut grade. The table-to-depth ratio is calculated by measuring the table’s diameter and comparing it to the diamond’s overall depth. An ideal round brilliant cut diamond typically has a table size that falls within a certain percentage range of its overall diameter, usually between 53% and 58% for optimal brilliance.

Ideal Table Size: For round brilliant cut diamonds, an ideal table size typically falls between 53% and 58% of the overall diameter, balancing light reflection and maximizing brilliance.
Large Table: A diamond with an excessively large table relative to its depth may reflect less light, leading to a loss of brilliance and a flat appearance. In contrast, a smaller table could result in a diamond that looks darker or less reflective.
Table in Fancy Shapes:
While the table is a key feature in all diamonds, it is especially important for round brilliant cut diamonds. In fancy-shaped diamonds, such as princess, emerald, and asscher cuts, the table may vary slightly in shape and size to accommodate the unique proportions and angles of each cut. However, the role of the table in influencing light entry and brilliance remains consistent across all diamond shapes.

DCLA and Table Quality:
The Diamond Certification Laboratory of Australia (DCLA) is one of the leading authorities in diamond grading and certification, particularly within the Australian market. When a diamond is graded by DCLA, the table is assessed as part of the overall cut grade. DCLA uses a comprehensive set of criteria to evaluate all facets of the diamond, including the table facet.

The table is evaluated for size, symmetry, and alignment, ensuring that it contributes to the overall quality of the cut and the diamond’s ability to reflect light properly.
DCLA reports provide detailed information about the table size in relation to the diamond’s total diameter, helping consumers and investors understand how the table contributes to the diamond’s brilliance and overall visual appeal.
DCLA also measures the proportions of the table and other facets, ensuring that the diamond meets industry standards for ideal proportions. The laboratory’s expertise in evaluating the table facet, alongside other critical attributes like crown angle and pavilion depth, ensures that each diamond receives a thorough and accurate grading report that reflects its true quality.

Table and Diamond Certification:
In the grading report issued by DCLA, the table facet is one of the important details that helps determine the diamond’s overall cut grade. Since the cut is a significant factor in determining the diamond’s beauty and value, the size, proportions, and finish of the table are carefully examined. A well-proportioned table enhances the diamond’s light performance, while an incorrect or poorly finished table can result in suboptimal visual appeal.

In addition to the table’s size, the report may also include additional information about the table’s polish, symmetry, and overall surface quality, as these factors all influence the diamond’s final appearance.

The table is a crucial facet in determining a diamond’s overall beauty and brilliance. Its size, shape, and position play a vital role in how the diamond interacts with light and contributes to the diamond’s overall sparkle and visual appeal. Whether it is a round brilliant cut diamond or a fancy shape, the quality and proportions of the table can significantly affect the diamond’s grade and value. The DCLA ensures that diamonds are thoroughly assessed and accurately graded, with special attention to the table’s impact on the diamond’s overall cut quality and performance.

July, 2017February, 2025

Table Size

Table size refers to the measurement of the table facet of a diamond, which is the large, flat surface located on the top of the stone. It is expressed as a percentage of the diameter of the diamond. The table size is a crucial factor in determining the overall appearance and brilliance of the diamond. It plays an essential role in balancing brilliance (the white light reflected from the diamond) and dispersion (the colourful flashes of light that come from the diamond’s facets).

Table Size and its Impact on Brilliance and Fire:
Brilliance: A well-proportioned table allows for an optimal amount of light to enter the diamond, reflect off the facets inside, and return to the viewer’s eye. The table size is an essential factor that helps to achieve maximum brilliance. When the table is too large, more light may leak out from the bottom of the diamond, reducing brilliance. A table that is too small may limit light reflection, resulting in a dull appearance.
Dispersion (Fire): Dispersion is the colourful flashes of light that a diamond emits when it is moved or viewed under direct light. The table size also affects how much dispersion is visible. A properly proportioned table will allow for the best balance between brilliance (white light) and fire (colourful flashes). If the table size is too large, it may decrease the intensity of the dispersion, as the light may not be effectively refracted and split into different colours.
How Table Size is Measured:
Table Size as a Percentage: Table size is typically expressed as a percentage, representing the diameter of the table facet in relation to the overall diameter of the diamond. For example, if the table diameter is 5mm and the overall diameter of the diamond is 8mm, the table size would be calculated as:
Table Size Percentage

Table Size Percentage=(85)×100=62.5%

This means the table facet makes up 62.5% of the total diameter of the diamond.
Ideal Table Size:
For round brilliant cut diamonds, the ideal table size typically falls within the 53% to 58% range of the diamond’s total diameter. This proportion allows for the best balance of light reflection and brilliance, ensuring the diamond appears vibrant and sparkling. When the table is within this ideal range, it enhances the diamond’s overall performance by optimising how it handles light.

Ideal Range: A table size between 53% and 58% is generally considered ideal for round brilliant cut diamonds. Diamonds with table sizes within this range tend to exhibit excellent brilliance and light performance.
Larger Table Sizes: A table size that is larger than 58% may reduce the amount of light that is reflected, resulting in lower brilliance. This can make the diamond appear flat and less lively.
Smaller Table Sizes: A table size smaller than 53% may limit the amount of light that enters the diamond, reducing its sparkle and making the diamond look darker or duller.
Table Size and Diamond Grading:
The table size is one of the factors assessed when determining the cut grade of a diamond, particularly in round brilliant cut diamonds. The cut grade reflects the overall quality of the diamond’s proportions, symmetry, and polish, and it has a significant impact on the diamond’s brilliance and value.

Proportions: Table size is a crucial part of the overall proportions of a diamond, and it works in conjunction with other factors such as crown angle, pavilion depth, and girdle thickness to determine the overall quality of the cut.
Diamond Certification: Leading diamond grading laboratories, such as the DCLA (Diamond Certification Laboratory of Australia), carefully assess the table size when providing a grading report. They ensure that the table size falls within an acceptable range for the diamond’s shape and type to guarantee the best possible visual performance.
Fancy-Shaped Diamonds and Table Size:
While table size is most commonly associated with round brilliant cut diamonds, it also applies to other fancy-shaped diamonds, such as emerald cut, asscher cut, princess cut, and oval cut diamonds. However, for fancy shapes, the ideal table size may vary depending on the shape and the proportions of the diamond. For example:

Princess Cut Diamonds: In a princess cut diamond, the table size is usually larger relative to the overall size, often in the 60% to 70% range. This helps to achieve the maximum brilliance and visual appeal.
Emerald Cut Diamonds: Due to their step-cut faceting, emerald cut diamonds tend to have a larger table relative to their overall size, often ranging from 60% to 70% as well. The larger table enhances the clarity of the diamond, allowing the observer to better appreciate its internal characteristics.
Factors Affecting Table Size:
Several factors can influence the size of the table facet on a diamond:

Cutting Style: The cutting style of the diamond affects the table size. Round brilliant cuts are often cut with a smaller table, while other cuts like princess and emerald may have larger tables.
Diamond Size: Larger diamonds often have larger table sizes, as their proportions allow for more substantial table facets without sacrificing the diamond’s brilliance.
Manufacturer Preferences: Some diamond manufacturers may adjust the table size to meet specific aesthetic or performance goals, influencing the final appearance of the diamond.

The table size of a diamond is a crucial factor that significantly influences its brilliance and fire. It is measured as a percentage of the diamond’s overall diameter, and its proper proportion ensures the diamond displays optimal light performance. For round brilliant cut diamonds, the ideal table size typically falls within the 53% to 58% range, although fancy-shaped diamonds may have varying table sizes depending on their unique cutting styles. Properly balanced table size, along with other critical cut factors, contributes to a diamond’s overall beauty, value, and appeal. The DCLA and other leading certification labs evaluate table size as part of the comprehensive cut grading process, ensuring that the diamond performs to its fullest potential.

July, 2017February, 2025

Step Cut

A step cut is a style of diamond cutting that creates a distinctive look with rows or steps of elongated facets. These facets run parallel to the girdle of the diamond on both the crown (the upper portion) and the pavilion (the lower portion). The step cut is known for its classic, elegant appearance and is often used in diamonds with larger surface areas.

Key Features of Step Cut Diamonds:
Faceting Style: The defining characteristic of the step cut is the linear arrangement of facets, which resemble steps or rows. These elongated facets create a staircase-like effect, with the facets running parallel to the girdle of the diamond. This cut contrasts with the brilliant cut, which features numerous triangular and kite-shaped facets to reflect light in a more dynamic way.

Popular Step Cuts: Two of the most famous step cut diamond shapes are the emerald cut and the baguette cut:

Emerald Cut: The emerald cut is a rectangular or square-shaped diamond with cut corners. It features large, rectangular facets that showcase the diamond’s clarity and colour. The emerald cut is known for its elegant, understated beauty.
Baguette Cut: Typically smaller and more elongated, the baguette cut features long, rectangular facets and is often used as an accent stone or in vintage-style jewellery.
Facets and Symmetry: In a step cut, the facets are typically rectangular and arranged in a way that each one is aligned with the others, creating a step-like appearance. These facets are often fewer in number than those found in brilliant cuts, which gives step-cut diamonds a more minimalist and elegant appearance.

Clarity Emphasis: Step cuts, particularly the emerald cut, are often chosen for diamonds with high clarity because they showcase internal inclusions more prominently than a round brilliant cut. The large, flat facets on step-cut diamonds allow for a clearer view into the diamond, making it important to choose a stone with minimal visible flaws for the best visual appeal.

Light Reflection: Unlike brilliant cuts, which are designed to reflect light in many directions to create sparkle, the step cut focuses on creating a more subdued, reflective appearance. The large facets reflect light in a more linear way, and while step-cut diamonds might not have the same intense sparkle as a round brilliant cut, they often display a unique glow that comes from the reflection of light off their smooth, flat surfaces. This makes step-cut diamonds more suited for those who appreciate elegance and clarity over sparkle.

Advantages of Step Cut Diamonds:
Clarity Visibility: Step cuts are perfect for diamonds with excellent clarity because they allow you to see the diamond’s interior more clearly. This cut tends to highlight a diamond’s cleanliness and colour.

Sophisticated and Timeless: The elegant, understated look of step-cut diamonds makes them a favourite choice for those who prefer a more classic and timeless design. They often lend themselves to vintage-style or art-deco designs.

Better for Larger Stones: Step cuts tend to work well with larger diamonds because they allow the stone’s size to be appreciated without excessive light dispersion, which can make smaller diamonds appear less impressive. The open facet structure in step cuts can give larger diamonds a cleaner and more sophisticated appearance.

Disadvantages of Step Cut Diamonds:
Less Sparkle: While step-cut diamonds still possess beauty and brilliance, they do not reflect light in the same way that brilliant-cut diamonds do. The less intense sparkle can make them less desirable for those who prefer the flashy brilliance associated with modern cuts.

Visibility of Inclusions: Step cuts can make internal inclusions or imperfections more visible due to the large, open facets. Therefore, diamonds with higher clarity are preferred for step-cut styles to avoid any noticeable flaws.

The step cut is a refined and elegant diamond cutting style that emphasises clarity and colour over intense sparkle. With its distinct rows of elongated facets running parallel to the girdle, step-cut diamonds (like the emerald and baguette cuts) offer a timeless aesthetic that appeals to those seeking sophistication and simplicity. This cut is particularly well-suited for larger diamonds and stones with high clarity, and while it may not produce the same level of sparkle as a brilliant cut, it offers a unique, understated beauty that is highly valued in vintage and classic jewellery designs.