How to Choose a High-Quality Lab-Grown Diamond: RAGAZZA’s Round Diamond Selection and Inspection Process
Updated: 9 hours ago
When selecting a high-quality lab-grown diamond, start by filtering according to your budget and the 4Cs, then compare proportion data and review actual diamond videos. Finally, verify the diamond’s transparency, colour, optical performance, and overall integrity through physical inspection and professional instruments. Each step answers a different question; together, they provide a more reliable basis for determining whether a diamond is worth choosing.
When you are comparing several lab-grown diamonds that are all 2 carats, D colour, VVS1 clarity, 3EX, and similarly priced, which one should you choose?
When sourcing diamonds and making recommendations to clients, RAGAZZA DIAMOND uses DAII™ to analyse the data of shortlisted diamonds, combined with video review, physical inspection, an ASET Scope, and a Hearts & Arrows viewer to assess quality step by step. Using round brilliant-cut lab-grown diamonds as an example, this article shares our practical diamond selection process and helps you understand what to look for and what questions to ask when comparing diamonds.
Table of content
1. Define Your Budget, Size and Quality Goals
RAGAZZA’s supply database covers more than 200,000 lab-grown diamonds, with availability and inventory changing as transactions and data are updated. With such a wide selection, the first step is to determine your budget and decide how to balance size and quality.
Some buyers prioritise a larger diamond within their budget; others focus on value for money, while some have already decided on a specific carat size and want to maximise quality within that range. We first understand these priorities and then set the appropriate screening criteria.
For example, using a loose diamond budget of approximately HK$10,000 as a selection example, we can set the following targets:：
Specification | Example Criteria |
Diamond Type | Lab-Grown Diamond |
Shape & Cut | Round Brilliant Cut |
Carat Weight | Approximately 2 carats |
Colour | D |
Clarity | IF |
Cut, Polish & Symmetry | Excellent (3EX) |
Grading Report | IGI |
The above is an example to illustrate the screening process. Actual pricing and availability are subject to confirmation at the time of enquiry. The loose diamond budget does not include the setting or mounting costs. You may also adjust the colour, clarity, or carat range according to your preferences.
After the initial screening, we verify the certification details of the shortlisted diamonds, including the lab-grown diamond designation, measurements, proportions, and grading. If multiple diamonds still meet the criteria, we proceed to the next stage of comparison.
2. Use DAII™ to Compare Diamonds Within the Same Grade
Even when carat weight, colour, clarity, and cut grades are similar, round diamonds can still differ in table percentage, total depth, crown angle, pavilion angle, and other proportions. These differences are worth analysing further when selecting a diamond.
The DAII™ Diamond Quality Index is a data analysis model developed by RAGAZZA for diamond selection. It evaluates 16 indicators covering colour, clarity, cut, polish, symmetry, proportions and angles, fluorescence, girdle, culet, and grading report systems, helping us compare the quality of shortlisted diamonds.
Continuing with the previous example, among diamonds that meet the criteria of approximately HK$10,000, around 2 carats, D colour and IF clarity, we compare their DAII™ scores and prioritise candidates with higher scores for further evaluation.
A higher DAII™ score does not necessarily mean a higher price. Pricing is also influenced by factors such as grading laboratory, availability, and individual quotations. Therefore, among diamonds with similar prices, there may still be opportunities to find a diamond with more favourable proportions and cut-related specifications.
This step allows us to narrow down the selection efficiently. We then use diamond videos and physical inspection to verify the advantages reflected in the data, as well as details that cannot be fully captured by the score alone.
3. Review Actual Diamond Videos to Assess Transparency and Facet Performance
The diamond videos on the RAGAZZA website show actual footage of the corresponding diamond. Even when different videos appear similar, careful observation during rotation can reveal important details.
We first check for any visible inclusions, then assess whether the diamond appears clear and transparent, looking for persistent milky or hazy areas, or localised cloudiness. Transparency is an important factor in our diamond selection process. Candidates with noticeable milkiness or haze that affects their appearance are excluded.
When reviewing footage, it is also important to consider image quality, lighting, background, and the cleanliness of the diamond’s surface. If a particular angle is unclear, we may request additional footage or inspect the diamond in person to avoid mistaking filming conditions for characteristics of the diamond itself.
Facet performance is another key consideration. We look at whether the facet outlines appear well defined, whether the pattern is well balanced, and how the light and dark areas change as the diamond rotates. Standard rotation videos can provide an initial understanding of the diamond’s appearance, while a full Hearts & Arrows assessment is carried out using specialised equipment.
For a more comprehensive view of a particular diamond, you can contact us to request additional footage from different angles or under different conditions, such as when held with tweezers, viewed in daylight, placed on a hand, or positioned on a white diamond card.
In the example above, IF stands for Internally Flawless, meaning that no internal inclusions are visible to a trained grader under 10× magnification. However, surface characteristics may still be present. Video inspection should therefore be used together with the grading report and physical inspection to verify clarity. GIA Diamond Clarity
4. Compare the Diamond’s Colour in Person and Check for Unwanted Tints
After completing the data and video screening, we further assess the diamond’s colour and transparency. For white lab-grown diamonds, we look for a clear, naturally colourless appearance. During inspection, the diamond is placed on a white diamond card under consistent and appropriate lighting and compared side by side with a colourless reference diamond, viewed from both the front and the back.
We focus on any undesirable blue, yellow, green, or grey tints, while also considering the overall appearance of both diamonds. Comparing two diamonds side by side can reveal subtle differences that may be difficult to notice when viewing a diamond on its own.
This is our physical verification of the diamond’s appearance, while the colour grade remains based on the grading report.
RAGAZZA excludes white lab-grown diamonds that show undesirable colour tints upon physical inspection.
5. Use an ASET Scope to Assess Light Return and Leakage
A diamond’s cutting proportions influence how light enters, reflects within, and exits the stone. When some light exits through the pavilion rather than returning effectively to the observer’s eye, it can create light leakage, the extent and location of which warrant further examination.
ASET stands for Angular Spectrum Evaluation Tool and is used to assess a diamond’s optical performance. It displays light return and contrast from different angles in different colours, helping us understand how the diamond handles light as a whole.
RAGAZZA uses an ASET Scope to examine shortlisted round diamonds, focusing on:
Whether light return is evenly distributed.
Where light leakage is concentrated and whether the affected areas are significant.
Whether the performance of the centre and edges is well balanced, and whether any areas require further inspection.
Proper interpretation requires an understanding of what the colours represent. For example, blue in an ASET image indicates areas of contrast and should not be interpreted directly as light leakage. A diamond’s appearance naturally includes a balance of light and dark areas, so cut quality should not be judged simply by assuming that “the brighter the entire diamond, the better.
Even when a grading report assigns an Excellent or Ideal cut grade, we still examine the actual distribution of light. DAII™ helps us identify candidates with more favourable data, while ASET allows us to further evaluate the physical diamond. The two can therefore be used together as complementary references.
6. Use a Hearts & Arrows Viewer to Assess Optical Symmetry
Hearts & Arrows is a pattern displayed by round brilliant-cut diamonds under a specialised viewer, resulting from the arrangement of their facets and optical symmetry. From the top, the arrow pattern can be observed; when the loose diamond is flipped over, the heart pattern becomes visible.
We examine the diamond from both sides:
View | Key Check |
Top Eight Arrows | Clarity, alignment, and uniformity |
Bottom Eight Hearts | Completeness, consistency, spacing, and symmetry |
The diamond must be properly positioned and aligned before inspection to avoid distorted patterns caused by tilting or misalignment. If noticeable asymmetry, inconsistent heart sizes, or incomplete patterns remain after correct positioning, we conduct further evaluation.
Clear and well-defined Hearts & Arrows patterns are an important reference when assessing precision cutting. They primarily indicate optical symmetry, while overall quality should also be evaluated together with transparency, colour, light return, and diamond integrity. GIA also notes that a high degree of optical precision does not necessarily result in superior optical performance, so each inspection serves a different purpose.
7. Use 10× Magnification to Inspect the Diamond Upon Arrival
Videos and grading reports document the diamond’s condition at the time of filming and grading. Once the diamond arrives, we use 10× magnification to confirm that the physical stone matches the original records and to check for chips, scratches, or other damage.
The culet is one key area of inspection. Located at the bottom of the diamond, a chip may affect its appearance when viewed from the top. We inspect the culet from multiple angles and cross-check it from the face-up view; a white spot or reflection visible beneath the table does not, by itself, indicate culet damage.
The girdle and facet edges are also carefully examined. If the physical diamond shows characteristics not reflected in the video or grading report, we investigate further to determine whether they are surface contamination, data discrepancies, or subsequent damage.
This final step ensures that the diamonds we recommend and deliver meet our selection standards in their actual physical condition. Any unresolved issue that may affect quality or integrity must be addressed before the diamond is accepted.
8. Use 50× Magnification to Verify the Girdle Inscription and Condition
In addition to examining the diamond’s appearance, we use 50× magnification to inspect the laser inscription on the girdle, confirming that the inscription is clear, the number matches the grading report, and the details correspond with the grading laboratory’s official records.
We also examine the area around the inscription and the entire girdle for unusual abrasions, overlapping inscriptions, or other marks that may require further verification.
When inspecting diamonds brought in by clients, RAGAZZA has encountered unusual marks on the girdle. In such cases, we consider whether they may be related to subsequent processing, repolishing, or changes to the inscription, and conduct further verification.
Unusual marks alone do not prove damage, reprocessing, or forgery; likewise, a clear girdle inscription should be verified together with other supporting information. We focus on whether the physical diamond, grading report, and related characteristics are consistent. If any concerns cannot be resolved, we will not accept the diamond.
9. A Checklist for Selecting a High-Quality Lab-Grown Diamond
When comparing diamonds, use the following questions to identify what information you already have and where you may need assistance from a diamond specialist.
Inspection Area | Key Questions |
Budget & Criteria | Budget range and diamond size? |
Certificate & Data | How do DAII™ scores differ among comparable diamonds? |
Actual Video | Is the transparency and facet definition clear? |
Colour Inspection | Is there any colour tint under consistent lighting? |
ASET Inspection | How is light return distributed? Where is light leakage concentrated? |
Hearts & Arrows | Are the hearts and arrows complete, clear, and uniform? |
Arrival Inspection | Are the culet, girdle, and facet edges intact? Any damage? |
Inscription & Identity | Does the girdle inscription match the official grading report? Are there any unusual marks? |
Observe and Compare Diamonds in Person at RAGAZZA
RAGAZZA’s diamond selection service combines database screening, DAII™ analysis, video review, and physical inspection. We aim to ensure that every recommended diamond has clearly identifiable strengths, has undergone the necessary checks, and meets the client’s budget and requirements.
Our showroom provides an ASET Scope and Hearts & Arrows viewer, allowing clients to observe diamonds in person with the assistance of our consultants. You can compare differences in light return, leakage, and optical symmetry, together with the diamond’s appearance to the naked eye.
You can first use the Choose Your Diamond page to filter diamonds by budget and specifications, then share your preferred diamonds with us for further analysis. You can also contact us to make an appointment, and our consultants will guide you through the quality of each diamond step by step.
Original content by RAGAZZA Diamond. All rights reserved. No unauthorized reproduction or use.
