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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.

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Rough Diamond

A rough diamond is a diamond in its natural state, exactly as it is found deep within the Earth. It has not yet undergone any form of cutting, polishing, or alteration. Rough diamonds are typically irregular in shape, with a variety of textures, colours, and surface conditions, ranging from clear and transparent to opaque and coloured.

These diamonds are generally discovered in kimberlite pipes (volcanic formations) or alluvial deposits (water-worn areas), and they are extracted through a process of mining. Once found, rough diamonds are carefully sorted and graded based on their size, shape, colour, and clarity before they are sent to gem cutters for transformation into polished stones.

Key Characteristics of Rough Diamonds
Shape:

Rough diamonds are typically irregular, with shapes that can range from octahedral (two pyramidal shapes joined together) to dodecahedral (a 12-sided form). These shapes are determined by the crystal structure of the diamond and can vary widely.
The rough shape is not intended for jewellery, and the gem cutters will plan how to cut the stone based on its natural geometry to maximise yield and minimise waste.
Colour:

Rough diamonds can appear in a wide range of colours, from colourless and transparent to shades of yellow, brown, or even rare colours such as blue, green, or pink.
The final colour of the diamond will depend on its internal structure and any trace elements present in the rough material. Some rough diamonds are even tinted due to the presence of minerals or impurities.
Clarity:

In their natural form, rough diamonds may have a variety of inclusions and blemishes, such as tiny air bubbles or mineral inclusions trapped within the crystal. These internal flaws are often visible to the naked eye or under magnification, though they can be reduced or eliminated during the cutting and polishing processes.
Size:

Rough diamonds vary greatly in size, from small pebbles to large stones weighing several carats. Larger rough diamonds are often considered more valuable, especially if they possess good colour and clarity, as they can be cut into high-quality finished diamonds.
The Journey of a Rough Diamond
Extraction:

Rough diamonds are mined from the Earth, typically through open-pit mining, underground mining, or alluvial mining (searching for diamonds in riverbeds or coastal regions). Mining companies extract the rough stones from kimberlite pipes or riverbeds, often using advanced technology to locate diamond deposits deep underground.
Sorting and Grading:

Once extracted, rough diamonds are sorted based on their size, colour, clarity, and shape. Each diamond is examined to determine its potential for cutting and polishing. Some rough diamonds are too flawed or small to be cut into gem-quality stones and may be used for industrial purposes instead.
The DCLA (Diamond Certification Laboratory of Australia) offers rough diamond services to help classify and grade rough diamonds. They use their expertise to evaluate the quality of rough diamonds and assist in planning the best course of action for cutting and polishing.
Cutting and Polishing:

After sorting, the rough diamond is sent to skilled gem cutters, who use advanced techniques and tools to transform the stone into its finished form. The cutting process involves careful planning to maximise the yield (the amount of diamond produced from the rough stone) while aiming to enhance the diamond’s brilliance, fire, and overall appearance.
The diamond may be cut into a variety of shapes, such as round, emerald, princess, or cushion, depending on the rough stone’s shape and quality.
Grading:

Once the diamond is cut and polished, it is then graded according to the 4 Cs – Carat, Colour, Clarity, and Cut. This grade determines the diamond’s final value, and certificates from recognised laboratories such as DCLA are used to authenticate the quality of the diamond.
Uses of Rough Diamonds
Gem-quality Diamonds:

The primary use of rough diamonds is for gemstone production, where they are cut and polished into diamonds for use in engagement rings, earrings, necklaces, and other high-end jewellery.
Industrial Diamonds:

Some rough diamonds, particularly those with significant imperfections, are not suitable for use in jewellery. These diamonds are used for industrial purposes, where their hardness is highly valued. Industrial diamonds are employed in applications such as cutting, grinding, drilling, and polishing, where the diamond’s extreme hardness makes it ideal for cutting or shaping other materials.

The rough diamond is the very first step in the life cycle of a diamond. Found in the earth in its natural form, it is then extracted, sorted, and carefully crafted into the sparkling gemstones that are valued in fine jewellery. Due to their rarity and the complexity of their transformation, rough diamonds represent both the mystery of nature and the skill of the craftsmen who shape them into stunning finished products.

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Pinpoints

Pinpoints Very tiny diamond crystal inclusions

Pinpoints are extremely small diamond crystal inclusions that are typically too tiny to distinguish their individual shapes, even under magnification. When viewed under 10x magnification, a single pinpoint appears as a minute, white or black “dot” within the diamond. While a single pinpoint is often insignificant and may not affect a diamond’s overall clarity or brilliance, multiple pinpoints grouped together can form a cloud—a hazy or milky area within the diamond that can impact its transparency and light performance.

These inclusions are a natural part of a diamond’s formation process and are commonly found in many diamonds. Depending on their number, size, and location, pinpoints can have varying effects on a diamond’s clarity grade. In some cases, when they are sparsely distributed, they have little to no visible impact. However, if they are densely clustered, forming a significant cloud, they may lower the diamond’s clarity rating and slightly reduce its brilliance by affecting how light passes through the stone.

Pinpoints are one of the many inclusions that gemologists assess when grading diamonds, and they are often documented on a diamond’s grading report issued by reputable gemological laboratories such as the GIA (Gemological Institute of America) or DCLA (Diamond Certification Laboratory of Australia).

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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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Octahedron

Rough diamond Octahedron

An octahedron is one of the most sought-after crystal shapes for rough diamonds, featuring eight triangular faces arranged symmetrically. This shape resembles two four-sided pyramids joined at their base, forming a perfect geometric structure. Due to its natural symmetry and efficient cutting potential, octahedral rough diamonds are highly desirable for diamond cutting and manufacturing.

Characteristics of an Octahedral Diamond
Crystal Structure: Composed of eight equilateral triangular faces
Formation: Forms naturally under high pressure and heat within the Earth’s mantle
Symmetry: Well-balanced, making it one of the most efficiently cuttable rough diamond shapes
Occurrence: One of the most common and valuable rough diamond shapes found in nature
Why Octahedral Rough Diamonds Are Coveted
1. Ideal for Cutting Round Brilliant Diamonds
The octahedral shape is perfectly suited for cutting two round brilliant diamonds from a single rough stone, maximizing yield and minimizing waste.
Diamond cutters often cleave or saw the rough along its natural planes to create two symmetrical, high-quality diamonds.
2. Natural Growth of Diamonds
The octahedron reflects the cubic crystal system of diamonds, where atoms arrange themselves in the most stable geometric form.
Over millions to billions of years, carbon atoms bond in this shape under extreme pressure deep within the Earth.
3. High Clarity Potential
Since octahedral diamonds grow in a stable environment, they often develop with fewer inclusions compared to irregularly shaped rough stones.
Their internal structure is generally strong, reducing the risk of fractures during the cutting process.
Octahedral Diamonds in Cutting & Polishing
How Cutters Assess an Octahedral Rough Diamond:
Orientation: Experts determine the best way to cut the rough to achieve the highest carat yield.
Inclusion Mapping: If internal flaws are present, cutters adjust the cutting plan to eliminate or minimize them.
Cleaving/Sawing: The rough is often split along its natural grain to form two high-quality gemstones.
Common Diamond Cuts from an Octahedron:
Cut Style Why It’s Chosen for Octahedral Rough
Round Brilliant Uses the natural symmetry of the octahedron to produce two symmetrical stones
Princess Cut Retains a high percentage of the original rough weight
Cushion Cut Maximizes brilliance while preserving rough material
Octahedron vs. Other Rough Diamond Shapes
Rough Diamond Shape Description Cutting Potential
Octahedron Eight triangular faces, symmetrical High yield, excellent for round brilliants
Dodecahedron Twelve pentagonal faces, irregular More cutting challenges, lower yield
Macles (Twinned Crystals) Flattened, triangular shape due to twinning Often used for fancy cuts, less efficient for rounds
Cubo-octahedron Mix of cube and octahedron faces Good for step cuts like emerald or Asscher


The octahedron is the most desirable natural shape for rough diamonds due to its symmetry, high clarity potential, and efficient cutting yield. This structure allows diamond cutters to maximize the rough’s potential, often yielding two high-quality round brilliant diamonds from a single octahedral crystal. Its formation represents the natural stability of diamond growth, making it a prized find in the world of gemology.

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Natural Diamond

A natural diamond is a gemstone composed of crystallized carbon

A natural diamond is a gemstone composed of crystallized carbon that was formed deep within the Earth’s mantle under extreme heat and pressure over 1 to 3 billion years ago. Unlike lab-grown diamonds, which are created in controlled environments, natural diamonds are mined from the Earth and are considered one of the rarest and most valuable gemstones.

Formation of Natural Diamonds
Natural diamonds form 100–200 km (62–124 miles) below the Earth’s surface, where intense pressure (725,000+ psi) and high temperatures (1,100–1,400°C) cause carbon atoms to bond in a unique cubic crystal structure. These diamonds are then transported to the surface through volcanic eruptions, specifically via kimberlite pipes—ancient volcanic conduits that carry rough diamonds upward.

Characteristics of Natural Diamonds
Composition:
Made of pure carbon arranged in a tetrahedral lattice, giving diamonds their exceptional hardness.
Hardness (Mohs Scale 10):
The hardest known natural material, making it highly resistant to scratches and wear.
Brilliance & Fire:
Due to its high refractive index (2.42), a well-cut diamond reflects and disperses light, creating its signature sparkle.
Unique Inclusions & Imperfections:
Most natural diamonds contain inclusions (internal characteristics) and blemishes (surface characteristics) that serve as fingerprints of their natural origin.
Rarity & Value:
Large, flawless natural diamonds are exceptionally rare, making them highly valuable compared to lab-grown alternatives.
Types of Natural Diamonds
1. White (Colorless) Diamonds
The most sought-after diamonds, graded on a color scale from D (colorless) to Z (light yellow or brown).
The less color, the higher the value.
2. Fancy Color Diamonds
Natural diamonds can exhibit blue, pink, yellow, green, orange, and even red hues due to trace elements or structural irregularities.
Examples:
Blue diamonds (trace boron) – Example: The Hope Diamond
Pink diamonds (structural distortions) – Example: Argyle Pink Diamonds
Yellow diamonds (trace nitrogen) – Example: Tiffany Yellow Diamond
3. Industrial Diamonds
Low-quality natural diamonds used in cutting, drilling, grinding, and polishing tools due to their extreme hardness.
How Natural Diamonds Are Mined
Natural diamonds are extracted from the Earth using various mining techniques:

Kimberlite Pipe Mining (Primary Source)

Diamonds are found in kimberlite pipes, ancient volcanic conduits rich in diamond-bearing rock.
Mined using open-pit or underground methods.
Alluvial Mining (Secondary Source)

Diamonds eroded from kimberlite pipes are transported by rivers and accumulate in riverbeds or coastal areas.
Marine Mining

Specialized ships mine diamonds from the ocean floor, particularly off the coast of Namibia and South Africa.
How Natural Diamonds Are Identified
To distinguish a natural diamond from a lab-grown or synthetic diamond, experts use advanced testing and certification from recognized gemological labs like DCLA, GIA, and AGS.

Key Identification Methods:
Inclusions & Growth Patterns: Natural diamonds contain unique inclusions, such as tiny crystals, feathers, or graining patterns, absent in lab-grown diamonds.
Fluorescence & Phosphorescence: Some natural diamonds exhibit fluorescence under UV light, while lab-grown diamonds may show different reactions.
Spectroscopy & Advanced Testing: High-tech tools like FTIR (Fourier-transform infrared spectroscopy) and UV-Vis spectrometry help differentiate natural diamonds from synthetic or treated ones.
Natural Diamonds vs. Lab-Grown Diamonds
Feature Natural Diamond Lab-Grown Diamond
Formation Formed over billions of years in Earth’s mantle Created in weeks using HPHT or CVD methods
Origin Mined from the Earth Manufactured in a lab
Inclusions Natural growth patterns and inclusions Different internal characteristics, sometimes with metallic inclusions (HPHT)
Rarity Extremely rare, especially high-quality stones Mass-produced
Price Higher due to rarity Generally 50–70% cheaper
Resale Value Strong resale and investment value Limited resale market
Ethical Concerns Some concerns over ethical sourcing (unless from certified conflict-free sources) Considered conflict-free and more sustainable
Ethical & Sustainable Sourcing of Natural Diamonds
Concerns over “blood diamonds” (conflict diamonds) led to the Kimberley Process Certification Scheme (KPCS), which ensures that natural diamonds are ethically sourced and do not fund conflicts.

Reputable diamond companies, including DCLA-certified brands, focus on:

Conflict-free mining practices
Fair labor policies
Sustainable environmental impact reduction
Why Choose a Natural Diamond?
Timeless Value: Unlike lab-grown diamonds, natural diamonds retain strong resale and investment value.
Unique & One-of-a-Kind: Each natural diamond has its own history, inclusions, and growth patterns, making it a unique creation of nature.
Symbolism & Tradition: Used in engagement rings, heirlooms, and high jewelry, natural diamonds carry deep emotional and historical significance.

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Mohs Scale

The Mohs Scale of Hardness is a qualitative scale that ranks minerals based on their ability to resist scratching

The Mohs Scale of Hardness is a qualitative scale that ranks minerals based on their ability to resist scratching. Developed by German mineralogist Friedrich Mohs in 1812, the scale is widely used in geology, gemology, and material science to compare the hardness of different minerals and gemstones. It ranges from 1 (softest) to 10 (hardest), with each mineral capable of scratching those ranked below it while being scratched by those ranked above it.

Mohs Scale of Hardness – Ranking of Minerals
Mohs Hardness Mineral Common Comparison
1 Talc Very soft; can be scratched by a fingernail; found in talcum powder.
2 Gypsum Soft; can be scratched by a fingernail; used in plaster and drywall.
3 Calcite Can be scratched by a copper coin; found in limestone and chalk.
4 Fluorite Can be scratched by a knife blade; used in fluorine production.
5 Apatite Can be scratched by a steel nail; found in teeth and bones.
6 Orthoclase Feldspar Harder than glass; a common mineral in granite.
7 Quartz Can scratch glass and steel; commonly found in sand and gemstones like amethyst and citrine.
8 Topaz A durable gemstone; harder than quartz and feldspar.
9 Corundum Includes sapphires and rubies; extremely hard, only scratched by diamond.
10 Diamond The hardest naturally occurring substance; used in cutting tools and jewelry.
Understanding the Mohs Scale
The Mohs scale is ordinal, meaning the difference in hardness between minerals is not proportional. For example, diamond (10) is about four times harder than corundum (9), even though the scale suggests a difference of only one unit.
Some synthetic materials and alloys can exceed the hardness of natural minerals. For example, tungsten carbide and cubic boron nitride have hardness levels approaching that of diamond.
While hardness measures scratch resistance, it does not indicate a mineral’s toughness or resistance to breaking. Diamond, while the hardest mineral, is brittle and can be shattered by a sharp blow.
Mohs Scale and Gemology
In gemology, the Mohs scale helps determine the durability of gemstones for everyday wear. Harder stones (e.g., diamond, sapphire, ruby) are ideal for engagement rings and jewelry exposed to frequent wear, while softer stones (e.g., opal, pearl, turquoise) require extra care to avoid scratches.

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Lower-Girdle Facets

The lower-girdle facets are crucial elements in the overall symmetry and brilliance of a diamond. These triangle-shaped facets are located on the pavilion of the diamond, directly adjacent to the girdle, which is the outer edge of the diamond. The pavilion refers to the bottom part of the diamond, below the girdle, which is responsible for reflecting light back through the crown and into the observer’s eye.

Position and Structure
Location: The lower-girdle facets are positioned on the pavilion of the diamond, near the girdle. They are situated just below the main facets of the pavilion, including the main pavilion facets, which are the large, flat surfaces that reflect light into the crown.

Shape: These facets are typically triangle-shaped, although their size and exact proportions can vary depending on the cut of the diamond. In some diamonds, these lower-girdle facets may be slightly elongated or modified, but they usually maintain a triangular form.

Function: The primary function of the lower-girdle facets is to help direct light in the diamond, contributing to its brilliance and scintillation. These facets work by reflecting light that enters the pavilion from below, which then bounces back through the crown of the diamond, creating the visual effects that make diamonds sparkle. The interaction between the light and these facets is essential in maximizing the diamond’s overall visual appeal.

Impact on Diamond Performance
Brilliance:

The brilliance of a diamond is its ability to reflect white light. The lower-girdle facets play an important role in this by directing light from the pavilion back into the crown. When the light is properly reflected, it bounces back to the viewer’s eye, enhancing the diamond’s brightness.
Scintillation:

Scintillation refers to the flashes of light that occur when a diamond moves or is viewed from different angles. The lower-girdle facets help enhance scintillation by creating additional reflections and refractions of light. Their triangular shape and position allow them to catch light from various angles, contributing to the diamond’s overall sparkle.
Symmetry:

Properly aligned and symmetrical lower-girdle facets are essential to the overall symmetry of the diamond. When the facets are evenly proportioned, the diamond will have a more visually appealing appearance, with well-defined light reflections and a balanced sparkle. Any irregularities in the alignment or shape of these facets can lead to an uneven distribution of light, reducing the diamond’s brilliance.
Grading the Lower-Girdle Facets
In diamond grading, the quality of the lower-girdle facets is considered as part of the overall cut grade, which evaluates how well the diamond has been shaped and proportioned to maximize its brilliance, fire, and scintillation. Some of the factors that affect the grading of the lower-girdle facets include:

Size and Proportion:

The size and proportion of the lower-girdle facets should be well balanced with the other facets of the diamond, including the main pavilion facets and the upper girdle facets. Proper proportions contribute to the diamond’s overall symmetry and visual appeal.
Symmetry:

Symmetry is one of the key components of diamond grading. Lower-girdle facets should be symmetrical, with uniform size and placement. Any misalignment or uneven facet sizes can disrupt the flow of light through the diamond and impact its overall performance.
Polish:

A well-polished surface on the lower-girdle facets enhances the diamond’s ability to reflect light. Poor polishing can lead to a dull appearance and reduce the brilliance of the diamond.
Role in Different Diamond Cuts
While lower-girdle facets are typically found in round brilliant cut diamonds, their placement and function can also be seen in other shapes that share similar cutting structures. However, the round brilliant cut diamond relies most heavily on the lower-girdle facets to achieve optimal light performance.

Round Brilliant Cut:

In the round brilliant cut, the lower-girdle facets are particularly important in creating the characteristic sparkle and fire that this cut is known for. The precise arrangement of these facets ensures that the diamond exhibits maximum brilliance and scintillation.
Other Fancy Cuts:

While fancy shapes like emerald, princess, or asscher cuts have different facet structures, they still rely on the principles of light reflection and refraction that are found in the lower-girdle facets of the round brilliant cut. For these shapes, the positioning and number of lower-girdle facets can vary, but their purpose remains the same: to enhance the diamond’s brilliance.
Impact of the Lower-Girdle Facets on Diamond Value
Diamonds with well-proportioned and well-cut lower-girdle facets typically have better light performance, meaning they will display more brilliance, scintillation, and fire. As such, diamonds with ideal or well-graded lower-girdle facets are generally considered more valuable because they are more visually appealing. Poorly proportioned or poorly cut lower-girdle facets can negatively affect the diamond’s performance, reducing its overall desirability and value.

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Knot

A knot is a specific type of inclusion found within diamonds. It refers to an included crystal or foreign material that is embedded within the diamond, and in certain cases, it extends all the way to the surface of the stone, disrupting the clarity of the diamond. The knot can sometimes result in a visible raised or burnt area on the diamond’s surface, which may affect both the diamond’s appearance and its overall value.

Formation and Characteristics of a Knot
A knot is formed when a crystal or a foreign material becomes trapped within the diamond during its crystallization process. These inclusions are often caused by other minerals, such as garnet, graphite, or pyrite, which can become incorporated into the diamond’s crystal structure as it forms deep within the Earth’s mantle. These inclusions, when they grow to a size large enough and reach the surface of the diamond, are identified as knots.

The key characteristics of a knot include:

Size: Knots can vary in size, but they are generally larger than many other types of inclusions.
Shape: A knot is often irregularly shaped, with rough edges that can be visible within the diamond.
Visibility: When a knot reaches the surface, it may be visible to the naked eye or under magnification, depending on its size and location.
Effect of a Knot on Diamond Clarity
Inclusions, including knots, are important factors in determining the clarity grade of a diamond. The presence of a knot can significantly reduce a diamond’s clarity, depending on its size, location, and visibility. Since clarity is one of the key factors in diamond grading, knots are generally considered undesirable, especially if they are prominent or affect the overall appearance of the diamond.

The primary impacts of a knot on clarity are:

Lower Clarity Grade: Knots are typically graded as part of the diamond’s clarity assessment. A diamond with a visible knot on the surface may be downgraded in clarity compared to a similar diamond with fewer inclusions or no knots.
Potential for Weakening the Diamond: While knots do not always affect a diamond’s durability, they can sometimes create weak points. If a knot is close to the surface, it may potentially make the diamond more susceptible to damage, such as chipping or cracking.
Visual Appearance of a Knot
When a knot breaks through the surface of the diamond, it can sometimes leave a visible mark, which could be a slightly raised area or a burnt-looking spot. These marks can appear darker or different in texture than the surrounding surface of the diamond. In some cases, knots may appear as small, black or dark spots, particularly if the included crystal is dark or opaque.

Since the surface of a diamond is a key aspect of its overall appearance, the presence of a knot can have an impact on how light interacts with the stone, potentially reducing its brilliance or sparkle. However, in some cases, the knot may be positioned in such a way that it does not significantly affect the diamond’s aesthetic quality.

Impact of Knots on Diamond Value
Knots can reduce a diamond’s market value, as they negatively affect its clarity and appearance. The extent of the impact on value depends on several factors:

Size of the Knot: Larger knots, particularly those visible to the naked eye, will generally result in a more significant reduction in value.
Location of the Knot: Knots located in more visible areas, such as the crown or table, will have a greater impact on the diamond’s appearance and thus its value. Conversely, knots located on the pavilion (bottom) or near the girdle may be less noticeable.
Number of Knots: Diamonds with multiple knots may be valued lower than those with fewer or no inclusions. However, some diamonds may contain one or two small knots that do not significantly affect their overall appearance or value.
Knot vs. Other Inclusions
While a knot is a relatively specific type of inclusion, it is useful to compare it with other types of diamond inclusions:

Crystal: Similar to a knot, a crystal is an inclusion of another mineral within the diamond. However, unlike a knot, a crystal does not necessarily break through the surface of the diamond.
Feather: A feather is another inclusion that can sometimes reach the surface of the diamond. Unlike knots, feathers are typically fissures or cracks in the diamond that may or may not affect the clarity grade.
Needle: A needle inclusion is a thin, elongated inclusion that does not typically reach the surface of the diamond, and thus may not be as impactful as a knot.
Treatment of Knots
In some cases, diamond cutters may attempt to minimise the visual impact of a knot by carefully positioning it or by using techniques like laser drilling to remove or reduce the visibility of inclusions. However, the presence of a knot often cannot be completely eliminated, particularly if the knot is close to the surface.

Additionally, some diamonds with prominent knots may be treated by laser inscription, which may help with traceability but will not alter the presence of the knot itself.