Category: Glossary

The diamond depth percentage is a key measurement used to evaluate the proportions of a diamond. It expresses the depth of the diamond as a percentage of its average diameter (width) and is essential in determining how well the diamond reflects light.

The formula for calculating the depth percentage is:

Depth Percentage=(Average Diameter of the DiamondDepth of the Diamond​)×100

Depth Percentage Range:
Ideal Range: For a round brilliant cut diamond, the depth percentage typically falls between 59% and 62.5%. This range provides a good balance between size and brilliance, ensuring that the diamond reflects light well while maintaining an appropriate size.

Shallow Depth: If the depth percentage is below 59%, the diamond may be considered shallow. This can cause light to leak out of the sides, resulting in reduced brilliance and a lackluster appearance.

Too Deep: A depth percentage greater than 62.5% can indicate that the diamond is too deep. This often leads to a smaller appearance for the carat weight, and may also reduce brilliance, as light escapes from the bottom of the diamond.

Ideal Proportions for Round Brilliant Diamonds:
Depth percentage: 59% to 62.5%
Table percentage: 53% to 58% (the percentage of the diamond’s top surface)
When considering diamond depth percentage, it’s important to also take other aspects of the diamond’s proportions into account, like the table percentage, crown angle, and pavilion angle, as they all work together to determine the diamond’s overall appearance and brilliance.

A diamond is a precious gemstone composed of carbon atoms arranged in a crystal lattice structure, which gives it remarkable hardness and brilliance. It is the hardest naturally occurring material on Earth, making it highly prized not only for its beauty but also for its durability. Diamonds are formed deep within the Earth’s mantle under extreme heat and pressure over millions of years.

Key Features of Diamonds:
Hardness: Diamonds are rated 10 on the Mohs scale of hardness, meaning they are the hardest substance known to man. This makes them ideal for use in jewelry, especially rings and other items subject to daily wear.

Brilliance: The unique structure of diamonds allows them to reflect and refract light in a way that creates their signature sparkle. The brilliance is largely determined by the diamond’s cut, which influences how light interacts with the stone.

Color: While diamonds come in a variety of colors, the most valued diamonds are those that are colorless or near-colorless. The Gemological Institute of America (GIA) grades diamonds on a color scale from D (colorless) to Z (light yellow or brown). However, diamonds also come in fancy colors such as pink, blue, and yellow, which are graded on a different scale.

Clarity: This refers to the presence of internal or external imperfections, known as inclusions and blemishes, respectively. The fewer imperfections a diamond has, the higher its clarity grade. Clarity grades range from Flawless (FL) to Included (I1, I2, I3).

Carat Weight: The size of a diamond is measured in carats (ct), where 1 carat equals 0.2 grams. Larger diamonds are rarer and often more valuable due to their size.

Cut: The cut refers to how a diamond has been shaped and faceted, influencing how well it reflects light. The quality of the cut, rather than its shape (e.g., round, oval, princess), has the biggest impact on a diamond’s brilliance.

Types of Diamond Cuts:
Round Brilliant: The most popular and widely used cut, known for its maximum brilliance and sparkle.
Princess: A square or rectangular shape with pointed corners, offering a modern and sharp look.
Emerald: Known for its step-cut facets, which highlight clarity and offer a sophisticated, elegant style.
Cushion: A blend of round and square, with soft, rounded corners and large facets, giving a vintage feel.
Oval: An elongated shape, offering a unique, sophisticated appearance and a larger appearance compared to round diamonds of the same carat weight.
Natural vs. Lab-Grown Diamonds:
Natural Diamonds: Formed over millions of years under high pressure and temperature deep within the Earth.
Lab-Grown Diamonds: Created in a laboratory using high-pressure, high-temperature (HPHT) or chemical vapor deposition (CVD) methods, which replicate the natural process. They are chemically identical to natural diamonds but can be more affordable.
Uses of Diamonds:
Jewelry: Diamonds are most commonly used in engagement rings, earrings, necklaces, and bracelets.
Industrial Applications: Due to their hardness, diamonds are used in cutting, grinding, and drilling tools.
Diamonds are not just symbols of luxury but also of endurance, making them ideal for celebrating significant milestones and relationships.

Diamond Cut for Weight refers to the practice of adjusting a diamond’s proportions to maximise its weight, sometimes at the expense of optimal cut quality. This process is typically seen when a diamond is cut to a specific carat weight, and the diamond’s proportions are altered to retain as much weight as possible from the original rough diamond. While it’s important to understand that this does not necessarily mean the diamond is cut poorly, the cut for weight can affect the diamond’s overall brilliance, sparkle, and light performance.

How Cut for Weight Affects a Diamond:
Weight Preservation:

Diamond cutters aim to preserve as much weight as possible from the original rough diamond. In some cases, this means making the diamond deeper or shallower than ideal to keep the carat weight intact.
A diamond that is cut to maximise weight may have proportions that are not ideal for light reflection, leading to less brilliance compared to a diamond cut to ideal proportions.
Depth vs. Table Size:

Shallow cuts (where the diamond is cut too wide with less depth) or deep cuts (where the diamond is cut very deep with a small table) are common in diamonds that are cut for weight.
Shallow-cut diamonds tend to have a larger table size, making them appear larger face-up, but they often lack brilliance since light escapes from the bottom rather than being reflected within the diamond.
Deep-cut diamonds may appear smaller for their weight because the table appears smaller, but they can reflect less light, leading to a less vibrant appearance.
Cut for Weight and Diamond Shape:

When cutting diamonds for weight, it is common to see a variety of shapes, including round and princess cuts, but some shapes are more prone to cut for weight than others.
For example, round brilliant diamonds are often cut for weight in ways that sacrifice the ideal proportions, leading to either a shallow or deep cut. Similarly, emerald cuts and asscher cuts may also be cut for weight, leading to larger faces with less depth.
Trade-offs Between Weight and Quality:

Cutting for weight can be a trade-off between achieving a desired carat weight and ensuring the diamond has optimal proportions to maximise its brilliance.
A well-cut diamond with excellent proportions will typically have the best brilliance and sparkle, but it may not be as large as a diamond that has been cut to maximise weight.
Light Reflection and Brilliance:

The cut quality of a diamond is directly linked to how well it reflects light. Ideal cut diamonds are designed to reflect as much light as possible, creating that sought-after brilliance and sparkle.
Diamonds cut for weight often have a lower cut grade because the proportions are not ideal for light performance, which can lead to a duller appearance.
Carat Weight vs. Appearance:

While diamonds cut for weight may appear larger due to the size of the table or girdle, they may not look as brilliant or sparkly as diamonds with ideal cuts. The key consideration is whether a larger diamond, cut for weight, is worth more to the buyer than one that is smaller but has superior light performance.
Choosing Between Weight and Quality:

Many buyers prefer diamonds that are cut to ideal proportions (even if they are slightly smaller in carat weight), as these diamonds offer superior brilliance and visual appeal.
If a buyer is looking for a specific carat weight, the trade-off may involve a less-than-ideal cut for weight.
The Importance of Cut Over Carat Weight:
When choosing a diamond, the cut often takes precedence over the carat weight in determining the overall beauty and value of the stone. A well-cut diamond, even if slightly smaller in weight, will typically appear more brilliant and attractive than a larger diamond with suboptimal proportions.
Diamonds that are cut for weight might appear larger or offer a higher carat weight, but their light performance and sparkle may be compromised.
How DCLA Evaluates Cut for Weight:
DCLA (Diamond Certification Laboratory of Australia) evaluates diamonds based on their cut quality rather than just focusing on weight. A DCLA report will provide precise details on the diamond’s proportions, symmetry, and polish, allowing buyers to understand the impact of weight-cutting decisions on the diamond’s appearance.
DCLA grades diamonds on cut based on a full spectrum of light performance analysis, including brilliance, fire, and scintillation. This is important because diamonds cut for weight may appear less brilliant, even if they weigh more.
Key Takeaways for Buyers:
Carat weight does not necessarily equate to a more beautiful diamond if the cut is compromised.
Diamonds cut for weight may have shallow or deep proportions that diminish brilliance.
It is generally better to prioritise a well-cut diamond with ideal proportions over a diamond that has been cut to maximize weight.
Always request a DCLA grading report to ensure that you understand the full cut quality, even when prioritising weight.
If you’re considering a diamond, it’s crucial to balance weight preferences with an understanding of the diamond’s cut quality and how it affects the diamond’s overall appearance. Would you like further guidance on understanding diamond proportions and how to select the best-cut diamond for your needs?

Diamond depth refers to the measurement of a diamond’s height, from the culet (bottom tip) to the table (top flat facet), as a percentage of its diameter. This is an important aspect of a diamond’s proportions and affects its overall appearance, including brilliance and sparkle.

The depth percentage is calculated as:

Depth Percentage=(Average Diameter Depth​)×100

Ideal Depth Range:
The ideal depth percentage typically ranges from 59% to 62.5% for round brilliant diamonds. A diamond within this range is generally well-proportioned, optimizing light reflection and sparkle.
Impact on the Diamond:
Too Deep: If the diamond’s depth is too high (above 62.5%), it may appear smaller than its carat weight suggests because more of the diamond is concentrated in the pavilion (bottom). It can also lead to a loss of brilliance, as light may escape from the bottom of the diamond.

Too Shallow: If the depth is too shallow (below 59%), the diamond can appear larger but may not reflect light as effectively. This can cause it to appear dull or lackluster, as light may escape through the sides.

The depth, along with other factors like the diamond’s table size, crown angle, and pavilion angle, plays a critical role in determining the diamond’s overall sparkle and visual appeal.

The cushion cut diamond is a popular diamond shape known for its rounded edges and square or rectangular outline, giving it a distinctive pillow-like appearance. This cut is a blend of the classic round shape and the square shape, offering a balance of both styles. It has been a beloved cut for centuries and has seen a resurgence in recent years, particularly in engagement rings.

Key Features of the Cushion Cut Diamond:
Shape:

The cushion cut diamond is typically square or rectangular, with rounded corners that resemble a pillow (hence the name). It can come in various ratios, where the length-to-width ratio determines whether the diamond appears more square or more rectangular.
The rounded corners give the cushion cut its soft and vintage look, making it a timeless and romantic choice.
Facets:

The cushion cut has a unique facet structure compared to other cuts. It often has 58 facets (the same as the traditional round brilliant cut), though some variations, such as the modified cushion cut, may have additional facets to enhance brilliance.
The facets on a cushion cut diamond create a larger, more noticeable sparkle, with the light bouncing around the stone in a way that gives it a vintage yet brilliant shine.
Types of Cushion Cut:

Standard Cushion Cut: The traditional cushion cut, with rounded corners and soft edges.
Modified Cushion Cut: A variation that uses additional facets to enhance brilliance. It can be cut with a modern look, featuring sharper corners and a more contemporary style.
Cushion Brilliant Cut: A cushion cut with a modern, brilliant-style facet arrangement, designed for maximum sparkle.
Appearance:

Cushion cut diamonds are known for their soft, romantic glow and are often preferred for their vintage and classic look. This cut is ideal for those who like the glitter of the round brilliant but want something that feels more unique and timeless.
Depending on the specific facet arrangement and cutting style, the cushion cut can have a brilliant appearance, creating a large amount of sparkle and fire, or a antique-style appearance with a more subdued, charming glow.
Popularity:

The cushion cut is especially popular in engagement rings, particularly for those who want a vintage or antique-inspired design. It has also been a favorite among celebrities and is seen in many high-profile engagements.
The cut’s resurgence in popularity is partly due to its combination of classic beauty and modern brilliance.
Durability:

The cushion cut diamond is generally quite durable because of its rounded corners. These corners are less prone to chipping compared to the sharp edges of other cuts, such as the emerald or asscher cuts.
The diamond’s pavilion depth (how deep it is from the table to the culet) can affect its overall durability and brilliance, so a well-proportioned cushion cut will ensure the diamond lasts over time.
Choosing the Right Cushion Cut:

Length-to-Width Ratio: The length-to-width ratio is a key consideration when selecting a cushion cut diamond. A ratio of 1.00 will result in a perfectly square cushion, while ratios above or below 1.00 will create a rectangular cushion shape. The ratio will influence the diamond’s overall appearance and is a matter of personal preference.
Cut Quality: The quality of the cut will have a significant effect on the diamond’s brilliance. Cushion cuts can be brilliant (emphasizing sparkle) or antique-style (more muted and charming). Look for diamonds with excellent or very good cut grades to ensure optimal light reflection and sparkle.
Clarity and Color: While cushion cut diamonds can hide inclusions and color better than other cuts due to their larger facets and the faceted structure, it is still important to check for clarity and color before purchasing.
Ideal Settings for Cushion Cut Diamonds:

Halo Setting: A cushion cut diamond in a halo setting (surrounded by smaller diamonds) is particularly popular, as it amplifies the appearance of the main diamond and adds extra sparkle.
Vintage and Classic Settings: The cushion cut diamond fits perfectly into vintage-style or antique-inspired rings, often with intricate detailing or milgrain edges around the band.
Solitaire Settings: Many people opt for a solitaire setting (a single diamond on the band) for a cushion cut diamond, allowing the diamond to be the main focus.
Brilliance and Sparkle:

The cushion cut is known for its good sparkle due to the faceting structure, but it may not exhibit the same level of fire (colored light reflections) as round brilliant cuts.
The brilliance of the cushion cut comes from the way light interacts with the larger facets. A well-cut cushion can shine brightly and produce beautiful flashes of light.
Cushion Cut vs. Other Cuts:

Round Brilliant vs. Cushion Cut: While round brilliant diamonds are typically the most brilliant (sparkling) due to their specific facet pattern, cushion cuts can offer similar sparkle with a softer, more vintage look.
Princess Cut vs. Cushion Cut: Princess cuts are square-shaped with sharp edges, providing a modern and angular look, while cushion cuts offer a softer, more rounded feel. The choice depends on personal style preferences.

Diamond Cut or Proportion refers to the quality of a diamond’s shape and symmetry, which directly influences its brilliance, fire, and overall aesthetic appeal. It’s one of the most important aspects of diamond grading and is separate from the diamond’s shape (e.g., round, princess, cushion). The cut is all about how well the diamond has been crafted and faceted from the rough stone, and how this craftsmanship maximizes its ability to reflect light.

Key Aspects of Diamond Cut/Proportion:
What is Diamond Cut?

Diamond Cut refers to how well a diamond has been shaped and faceted to reflect light, which impacts the diamond’s sparkle.
It involves the proportions (depth, width, angles) of the diamond and how they affect the way light enters, bounces around, and exits the diamond.
Cut does not refer to the diamond’s shape (such as round or square), but rather to the quality of the cutting process, including the diamond’s facets, symmetry, and polish.
The Importance of Cut:

A well-cut diamond reflects light more effectively, creating maximum sparkle and brilliance. A poorly cut diamond, even if it is of high-quality material, may appear dull or lifeless.
A well-cut diamond allows for optimal light performance. Light enters the diamond, reflects off the facets, and exits the top, creating a brilliant sparkle.
The 4 Cs and Cut:

The 4 Cs of diamond grading—Cut, Clarity, Colour, and Carat weight—are all important, but cut is often considered the most significant factor for a diamond’s visual appeal.
A diamond can be flawless in clarity and color, but if the cut is poor, it will not shine as brilliantly as a well-cut diamond.
Grading the Cut:

Ideal Cut: Diamonds with an “Ideal” cut are the best of the best, exhibiting maximum brilliance, fire, and sparkle.
Excellent Cut: Excellent cut diamonds also reflect light well and are often used interchangeably with “Ideal” cut in many grading reports.
Very Good Cut: A very good cut diamond still has excellent light performance, but there may be minor compromises in proportions compared to Ideal or Excellent.
Good Cut: Good cut diamonds still show decent sparkle, but they may not have as much brilliance as those graded Excellent or Ideal.
Fair and Poor Cuts: These diamonds lack the brilliance and sparkle that higher-quality cuts offer. Light is lost through the sides or bottom, resulting in a less brilliant appearance.
Key Elements of Cut/Proportion:

Table: The flat top surface of the diamond. The table size affects how much light is reflected inside the diamond.

Ideal Table Size: The table should typically be between 53-58% of the diamond’s diameter. A table that’s too large can cause light to leak out the bottom, and a table that’s too small may cause the diamond to appear dark or dull.
Depth: The height of the diamond from the culet to the table.

Ideal Depth: A diamond’s depth percentage (height divided by diameter) should fall between 59-62.5%. If the depth is too shallow, light will escape from the bottom, making the diamond less brilliant. If it’s too deep, light will exit from the sides, resulting in a dimmer appearance.
Crown Angle: The angle at which the upper portion (crown) of the diamond is cut. This influences how light enters and reflects within the diamond.

Ideal Crown Angle: For round brilliant diamonds, an ideal crown angle is generally between 34-35 degrees.
Pavilion Angle: The angle of the diamond’s lower portion, from the girdle to the culet. This also affects how light enters the diamond and contributes to its overall brilliance.

Ideal Pavilion Angle: Around 40.6-41.2 degrees for a round brilliant diamond.
Girdle: The outer edge of the diamond, where the top (crown) and bottom (pavilion) meet.

Ideal Girdle: The girdle should be neither too thick nor too thin, as extremes can affect the durability and light performance of the diamond.
Symmetry and Polish:

Symmetry refers to the precision of the diamond’s facets and how well they align. Good symmetry ensures that light is evenly reflected, contributing to the diamond’s brilliance.
Polish refers to the smoothness of the diamond’s surfaces. The better the polish, the more light the diamond can reflect.
Cut and Diamond Shapes:

The cut will vary slightly depending on the diamond shape. For example:
Round Brilliant Cut: Known for its excellent light reflection and maximum brilliance due to its specific proportions and symmetry.
Princess Cut: Features a square shape with sharp edges and also requires precise cutting for optimal brilliance.
Emerald Cut: Has a rectangular shape with a large table and fewer facets, focusing on clarity rather than brilliance.
Cushion Cut: Features rounded corners and is often designed with a more antique-style cut, which can affect its overall sparkle and brilliance.
Diamonds and Their Light Performance:

A diamond’s ability to perform with light is often referred to as its fire (the dispersion of light into rainbow colors), brilliance (the white light reflected from the diamond), and scintillation (the flashes of light as the diamond moves).
The cut of the diamond directly influences these factors. The angles, proportions, and symmetry all contribute to how effectively the diamond performs with light.
Evaluating Diamond Cut:

Ideal and Excellent cuts provide the best overall appearance and maximum brilliance.
A diamond with a good cut still offers decent brilliance but may be a bit less fiery or sparkly than an Ideal or Excellent cut diamond.
It’s crucial to evaluate a diamond’s cut based on specific cut grading criteria from a reputable grading laboratory like GIA, which assigns cut grades to diamonds based on measurements and performance.
Summary:
The diamond cut (or proportion) determines how a diamond interacts with light, influencing its brilliance, fire, and overall sparkle.
Key elements that affect cut include table size, depth, crown angle, pavilion angle, girdle thickness, and the overall symmetry and polish.
The cut has the most significant impact on a diamond’s appearance compared to other characteristics like clarity or colour, and diamonds with excellent cuts will appear the most vibrant and brilliant.
Grading: Diamonds are graded for cut as Ideal, Excellent, Very Good, Good, Fair, or Poor, based on their proportions, symmetry, and light performance.

Diamond Cut Grade is a key factor in determining a diamond’s overall beauty and value. It assesses how well a diamond has been shaped and faceted to maximize its ability to reflect light, creating brilliance and sparkle. A diamond’s cut grade is different from its shape (such as round, square, or oval) because it refers specifically to the quality of the craftsmanship involved in shaping and faceting the stone.

The Key Elements of Diamond Cut Grade:
Proportions:

The proportions of the diamond include the ratio of the table size (top flat surface), depth (the height of the diamond), and the girdle (the outer edge). These proportions must be balanced to ensure that light can enter, reflect, and exit the diamond optimally.
Symmetry:

Symmetry refers to how well the facets are aligned and arranged. Proper symmetry allows light to reflect evenly across the surface of the diamond, contributing to its brilliance.
Finish:

Finish refers to the quality of the polishing process. The finer the polish, the more light the diamond can reflect, enhancing its sparkle.
Diamond Cut Grades:
The cut grade can range from Excellent to Poor based on how well the diamond’s proportions, symmetry, and finish meet the ideal criteria. The scale used by most grading labs, including DCLA, is as follows:

Excellent Cut:

Diamonds with an Excellent Cut are considered the best. These diamonds reflect light in the most brilliant and dazzling way.
They have precise proportions, ideal symmetry, and a flawless polish, maximizing the sparkle and brilliance.
Ideal for: Those seeking the best possible appearance in terms of light performance.
Very Good Cut:

A Very Good Cut diamond reflects almost as much light as an Excellent Cut diamond, with only slight imperfections in the proportions or symmetry.
These diamonds still exhibit excellent brilliance, but may lack the extreme precision of an Excellent Cut.
Ideal for: Those who want a high-quality diamond at a slightly more affordable price point.
Good Cut:

A Good Cut diamond has visible differences in proportions, which can affect the diamond’s light reflection, but it still looks attractive with decent sparkle.
These diamonds may not exhibit the same level of brilliance as the top grades, but they offer good value.
Ideal for: Budget-conscious buyers who still want a well-cut diamond.
Fair Cut:

A Fair Cut diamond has more noticeable issues with proportions and symmetry that can reduce its ability to reflect light.
While still a diamond, it may appear less brilliant and duller than diamonds with higher cut grades.
Ideal for: Those seeking a lower-priced diamond, though it may not be the best in terms of light performance.
Poor Cut:

A Poor Cut diamond exhibits significant issues with proportions, symmetry, or polish, leading to poor light reflection and diminished brilliance.
The sparkle and fire are significantly reduced compared to higher-grade diamonds.
Ideal for: Typically, diamonds graded as Poor Cut are not recommended for purchasing, as they do not offer good visual appeal.
Factors That Influence Diamond Cut Grade:
Table Size: The table is the flat top facet of the diamond. If it’s too large or too small, it can affect the diamond’s brilliance.

Ideal Table Size: Typically between 53%-58% of the total diameter of the diamond.
Depth: The depth is the height of the diamond from the table to the culet. The depth percentage is the ratio of the diamond’s depth to its diameter.

Ideal Depth: Between 59%-62.5%.
Crown Angle: The crown is the upper portion of the diamond above the girdle. The crown angle influences how light is reflected from the diamond.

Ideal Crown Angle: Typically between 34-35 degrees for round brilliant cuts.
Pavilion Angle: The pavilion is the lower part of the diamond beneath the girdle. The pavilion angle helps determine how well the diamond reflects light.

Ideal Pavilion Angle: Around 40.6-41.2 degrees for round brilliant diamonds.
Girdle Thickness: The girdle is the outer edge of the diamond, and it should neither be too thin nor too thick.

Ideal Girdle Thickness: Neither too thin nor too thick, which allows for proper durability and light reflection.
Symmetry: Symmetry refers to how well the diamond’s facets match and align. Good symmetry ensures consistent light reflection and enhances the overall sparkle of the diamond.

Polish: The finish or smoothness of the diamond’s facets affects how light travels and reflects. A smooth and well-polished diamond reflects more light and appears more brilliant.

The Role of Cut in Diamond Value:
Cut is the most important factor in a diamond’s appearance. While colour, clarity, and carat weight are important, a poorly cut diamond will not appear as brilliant as a well-cut diamond, regardless of its other attributes.
A diamond’s cut grade can significantly impact its price. Diamonds with Excellent or Ideal cuts are typically more expensive due to their superior light performance and visual appeal.
DCLA’s Diamond Cut Grading:
The Diamond Certification Laboratory of Australia (DCLA) follows the international cut grading standards and provides a detailed analysis of a diamond’s cut, including the table size, depth, crown and pavilion angles, symmetry, and finish.
DCLA uses advanced gemological tools to measure and grade diamonds with precision, ensuring that each diamond receives an accurate and reliable cut grade.

Cubic Zirconia (CZ) is a synthetic gemstone that is often used as a diamond simulant. It is made from zirconium dioxide (ZrO₂) and is commonly used in jewelry as an affordable alternative to diamonds due to its striking resemblance to them.

Key Points about Cubic Zirconia:
Composition:

Cubic zirconia is composed of zirconium dioxide and is typically created through a synthetic process. The crystal structure of cubic zirconia is cubic, which is where it gets its name from.
Cubic zirconia is artificially manufactured in laboratories, making it more affordable and accessible compared to diamonds, which are naturally occurring.
Appearance:

Cubic zirconia is colorless and has a similar brilliance and sparkle to diamonds, which is why it’s often used in jewelry as a diamond substitute.
It can also be created in a variety of colors, such as pink, blue, green, and others, by adding different metal oxides during the manufacturing process.
While CZ can appear similar to a diamond at first glance, it lacks the same level of fire (colored light dispersion) and is generally less durable than a diamond.
Durability:

One of the biggest differences between cubic zirconia and diamonds is their hardness. Cubic zirconia has a hardness of 8 to 8.5 on the Mohs scale, whereas diamonds are the hardest natural substance, scoring a 10.
Because of this, cubic zirconia is more prone to scratching and wearing down over time, especially when compared to diamonds, which maintain their shine and surface integrity much longer.
Weight:

Cubic zirconia is heavier than diamonds. This means that a cubic zirconia stone of the same size will weigh more than a diamond of the same size. This weight difference can sometimes be noticeable when comparing stones of similar size and shape.
Cost:

Cubic zirconia is significantly more affordable than diamonds. While the price of diamonds can be quite high due to their rarity and the complexities involved in their formation, cubic zirconia is a much cheaper option and is widely available.
CZ is commonly used in fashion jewelry, where the appearance of a diamond is desired, but the cost of an actual diamond is not necessary or desired.
Clarity:

Cubic zirconia is often created in a way that makes it free of inclusions or very clean in appearance. Unlike natural diamonds, which often contain inclusions (called blemishes or inclusions), cubic zirconia typically has perfect clarity.
While diamonds can have unique inclusions that add to their value and identity, CZ’s flawless appearance can sometimes be a disadvantage in terms of authenticity because it lacks the natural imperfections that make diamonds unique.
Uses:

Jewelry: Cubic zirconia is often used in rings, earrings, necklaces, and bracelets as a diamond substitute. It’s particularly popular in engagement rings, wedding bands, and costume jewelry.
Affordable Alternative: People who want the appearance of a diamond but don’t want to spend the high cost may choose cubic zirconia as an alternative.
Optical Properties:

Brilliance: Cubic zirconia is known for its high brilliance (sparkle), as it reflects light well, similar to diamonds. However, it has a higher dispersion than diamonds, which means it can exhibit more colorful flashes of light, often seen as a rainbow effect.
Fire: Although cubic zirconia has more fire than a diamond, it is generally considered less desirable in this regard compared to the subtle, refined fire diamonds produce.
Maintenance:

Since cubic zirconia is softer and more prone to scratching, it may require more care and maintenance than diamonds. Over time, CZ can lose its luster due to scratches and build-up of oils and grime.
Regular cleaning is recommended to maintain its appearance, and it’s advised to store cubic zirconia jewelry separately to prevent scratches.
Distinguishing from Diamonds:

Despite its close resemblance to diamonds, there are several ways to distinguish cubic zirconia from diamonds, such as by examining the weight, hardness, fire, and brilliance.
Gemological Testing: Professional gemologists use specific tools, like a diamond tester or refractive index measurement, to accurately identify cubic zirconia from diamonds.
Summary:
Cubic Zirconia (CZ): A synthetic gemstone made from zirconium dioxide, used as a diamond simulant due to its similar appearance but lower cost.
Hardness: CZ has a hardness of 8-8.5 on the Mohs scale, much lower than diamonds (10), making it more susceptible to scratches.
Appearance: CZ is colorless and exhibits a high level of brilliance, but it has more fire than diamonds, often appearing to have more colorful flashes of light.
Cost: CZ is much more affordable than diamonds, making it a popular choice for fashion jewelry and costume pieces.
Durability: Less durable than diamonds due to its lower hardness, CZ can wear down and scratch more easily.