A diamond's beauty goes beyond its grade. Diamond 4C Buying Guide · GIA Reports · Matched-Pair Diamonds
From facet light performance and shape proportions to matching pairs, understand the quality shown on reports and find diamonds suited to wear. Make more confident choices for engagements, anniversaries, and everyday jewelry.
Start with your needs.
Different purposes call for different buying priorities. You do not need to decide on all 4Cs before you begin looking for a suitable diamond.
What are the 4Cs of diamonds?
The diamond 4Cs are Carat, Color, Clarity, and Cut. These four are widely used factors in evaluating diamond quality and help compare a diamond's specifications and characteristics.
GIA (Gemological Institute of America) established the modern diamond grading system. However, the 4Cs are not a pricing formula and cannot fully replace viewing the actual stone; shape, size, light performance, origin, and treatment status are also worth confirming.
- CutCut
- Proportions and cutting craftsmanship affect how a diamond reflects and refracts light.
- CaratCarat
- Measures weight, not face-up dimensions; one carat equals 0.2 grams.
- ColorColor
- White diamonds commonly use D–Z color grades to describe the depth of their color.
- ClarityClarity
- Evaluated based on inclusions and surface features, not simply on the degree of sparkle.
This page's explanation of D–Z color grades and standard round-diamond cut grades mainly applies to white diamonds within the corresponding ranges; colored diamonds and other types of reports require separate consideration.
Look at light performance first, then the numbers.
What makes diamonds appealing is not limited to the grades on a report. How the facets and proportions handle light affects the brightness, fire, and scintillation you actually see.
BrightnessThe white light reflected back by a diamond, creating a bright visual effect.
FireWhite light disperses into spectral colors, producing colored flashes under suitable lighting.
ScintillationThe changes in brightness and flashes that appear as the diamond, light source, or viewer moves.
Understand the differences to know how to choose.
Expand the four sections below to understand what the grades mean, common misconceptions, and what to compare when making an actual purchase.
01 Cut｜Cut Shape is the outline; cut quality is the expression of light performance and craftsmanship.
Cut does not equal Shape
Shape describes the outer outline, such as round, oval, pear, and emerald. Cutting style describes the arrangement of facets; Cut Quality involves proportions, cutting, and other quality factors.
GIA's standard overall cut grades apply to standard round brilliant diamonds in the D–Z color range and are Excellent, Very Good, Good, Fair, and Poor. These overall cut grades cannot be directly applied to fancy-shaped diamonds.
What should you look for when buying?
- First confirm the shape and cutting style; do not confuse either with cut quality.
- For round diamonds, refer to the applicable overall cut grade and also pay attention to proportions, polish, and symmetry.
- Fancy-shaped diamonds should be compared by outline, length-to-width ratio, brightness distribution, and videos of the actual stones.
- For oval, pear, and marquise shapes, pay attention to the appearance of any central dark area or “bow tie.”
- Even with the same report grade, it is worth comparing stones side by side under similar lighting.
02 Carat｜Carat Weight is not the same as size, and total weight is not the same as the weight of a single stone.
How much is one carat?
The carat (ct) is a unit of gemstone weight. One carat equals 0.2 grams, or 100 points. The Hong Kong jewelry market commonly expresses diamond weight in “carats” or “points.”
Diamonds of the same carat weight can have different face-up dimensions because of differences in shape and proportions. When comparing, check the measurements in millimeters rather than looking only at weight.
- Compare weight, length, width, and depth together.
- Consider wearing proportions in relation to the finger, earlobe, or setting size.
- Diamonds of the same weight can have different prices due to other quality factors.
- Do not overlook cut, appearance, or budget in pursuit of a round carat weight.
03 Color｜Color Understand color grades and compare how diamonds look when set and worn in real life.
D–Z color grades of white diamonds
GIA's D–Z color grades describe the depth of color in corresponding white diamonds, from colorless to more visibly tinted. Subtle color differences must be graded under controlled conditions and should not be judged from webpage photos alone.
| Color Grade | Group |
|---|---|
| D–F | Colorless · Colorless |
| G–J | Near Colorless · Near Colorless |
| K–M | Faint · Faint |
| N–R | Very Light · Very Light |
| S–Z | Light · Light |
04 Clarity｜Clarity Look at the nature and position of inclusions, not just the grade name.
Clarity grading considers the size, number, position, nature, and prominence of inclusions and surface features, usually based on observation under 10× magnification. Whether they are visible to the naked eye still needs to be determined for each individual diamond.
| Grade | English Name | The Concept of 10× Magnification |
|---|---|---|
| FL | Flawless | No inclusions or surface blemishes are visible to an experienced grader under 10× magnification. |
| IF | Internally Flawless | No inclusions are visible under 10× magnification, but surface blemishes may be present. |
| VVS1/VVS2 | Very, Very Slightly Included | Inclusions are extremely minor and are difficult for an experienced grader to see even under 10× magnification. |
| VS1/VS2 | Very Slightly Included | Inclusions are small and range from difficult to relatively easy to notice under 10× magnification. |
| SI1/SI2 | Slightly Included | Inclusions are easy to notice under 10× magnification; whether they are visible to the naked eye must be confirmed for each individual stone. |
| I1/I2/I3 | Included | Inclusions are obvious under 10× magnification and may affect transparency and brightness. |
Beyond the 4Cs, There Are Still Questions Worth Asking.
A diamond's identity, fluorescence, and wearing needs should not be obscured by a few grading letters.
Fluorescence
Fluorescence is the phenomenon of a diamond emitting light under ultraviolet radiation and is not part of the 4Cs. Fluorescence intensity alone cannot directly determine whether a diamond is hazy, nor should quality be decided solely by the fluorescence grade.
It is advisable to compare transparency and appearance under different lighting and consider them together with other quality factors and the actual quoted price.
Natural, Lab-Grown, and Treated
Natural diamonds and lab-grown diamonds have different origins. Lab-grown diamonds are not simulants; simulants are other materials that look similar to diamonds.
Before purchasing, confirm whether the diamond is natural or lab-grown and whether it has undergone any color or clarity treatment. Also review the applicable report and product disclosures.
Settings and Everyday Use
Rings, earrings, and pendants have different collision risks and wearing requirements. Although diamonds are highly durable, they can still be damaged by impact, so pointed corners and setting security deserve attention.
Considering shape, size, setting, and lifestyle together is more aligned with actual needs than simply pursuing the highest grade.
A Pair Means More Than Similarity.
Two individually beautiful diamonds do not necessarily create a harmonious pair. When comparing matched diamonds, consider specifications, outline, and light performance together.
- 01｜Outline and Proportions
- Compare the shape, length-to-width ratio, pointed corners, and overall outline for harmony.
- 02｜Face-Up Size
- In addition to carat weight, compare the millimetre measurements and visual size when placed side by side.
- 03｜Color and Clarity
- Confirm each stone's grade and note whether there are any obvious differences in color or transparency when worn.
- 04｜Brightness and Scintillation
- Observe the light performance and distribution of light and dark areas in the two diamonds under similar lighting and viewing angles.
Welcome to inquire with WILLS JEWELLERY about matched diamonds. Share your preferred shape, size, and earring design. Stone selection and cutting arrangements for individual matched pairs are subject to the actual product description.
How to Read a GIA Diamond Report
Reports make specifications clearer, while viewing the actual stone makes the choice more complete. They should complement rather than replace each other.
GIA diamond reports provide applicable identification and grading information; they are not market valuations and do not guarantee future appreciation.
The items listed may differ depending on the report version and diamond type. Refer to the individual report.
Report Check can verify whether the report details match the GIA database; you still need to confirm that the actual diamond matches the report. If a girdle inscription is present, it should also be checked together with other identifying features.
- Report Number and Date Verify the report identity and confirm that the report details correspond to the selected diamond.
- Shape and Cutting Style Check the shape and cutting style, and do not equate them with the Cut quality grade.
- Measurements and Carat Weight Measurements are usually given in millimetres and weight in carats; looking at both together gives a clearer understanding of actual size.
- Color, Clarity, and Cut Grade Check Color and Clarity; the overall Cut grade has a specific scope of application, and not all shapes and reports include the same items.
- Polish, Symmetry, and Fluorescence Understand Polish, Symmetry, and Fluorescence separately, and do not treat any one of them alone as a guarantee of appearance.
- Comments, Diagrams, and Other Notes Pay attention to treatment disclosures, inclusion information, and other notes. Different report formats may not contain the same diagrams.
Let the choice come back to how it is worn.
From a single center stone to delicate settings, a diamond's size, shape, and metal lines together create a piece of jewelry's proportions and character.
Buying Diamond Rings and Center Stones
Share your preferred outline, wearing proportions, and budget. Starting with the coordination of the center stone and setting, explore engagement, anniversary, or custom-design options.
Ask About Diamond Rings and Center Stones →Matched Diamonds
Find coordinated pair proportions, compare outlines, face-up size, and light performance, then match them with earring or other jewelry designs.
Explore Matched Diamonds →Everyday diamond jewelry
Starting with design and everyday wear, explore how diamonds look in rings, earrings, pendants, and bracelets.
Browse Diamond Collections →This page does not provide real-time inventory or fixed prices. Please confirm with a jewelry consultant before visiting or making payment whether a specific gemstone or piece is available for viewing.
Frequently Asked Questions About Buying Diamonds
Clarify common questions first, then decide which specifications are worth prioritizing for comparison.
What are the 4Cs of diamonds?
The 4Cs of diamonds refer to Carat weight, Color, Clarity, and Cut, the widely used factors for evaluating diamond quality. When purchasing, you should also confirm the shape, measurements, natural or lab-grown status, treatment status, and appearance of the actual stone.
Do one-carat diamonds always look the same size?
Not necessarily. One carat is a weight, not a size. Diamonds of the same weight can show different face-up sizes because of differences in shape and proportions. When comparing, check the millimetre measurements and wearing proportions together. One carat equals 0.2 grams, or 100 points.
Does 3EX equal Hearts and Arrows?
No. 3EX generally means that Cut, Polish, and Symmetry are all rated Excellent. Hearts and Arrows refers to an optical symmetry pattern under specific viewing conditions and is not synonymous with 3EX. Diamonds with the same 3EX grade may still have different proportions and light performance.
Are SI1 or SI2 clarity diamonds guaranteed to be eye-clean?
Not necessarily. Inclusions in SI1 and SI2 diamonds are easily noticeable under 10× magnification; whether they are visible to the naked eye must be individually confirmed based on the diamond's size, shape, the location and nature of the inclusions, and viewing conditions. “Eye-clean” is not an official GIA clarity grade.
Are diamonds with fluorescence necessarily bad?
No. Fluorescence is the phenomenon of a diamond glowing under ultraviolet light. Fluorescence intensity alone cannot directly determine whether a diamond appears hazy; compare transparency and appearance under different lighting conditions, taking other quality factors and the actual price quote into account.
Does a GIA report represent a diamond's price or guarantee appreciation?
No. A GIA report provides applicable identification and grading information; it is not a market valuation and does not guarantee future appreciation. Report Check can verify whether the report details match GIA's database, but you must still confirm that the actual diamond matches the report.
What should I compare when buying a matching pair of diamonds?
In addition to comparing their respective weight, color, and clarity, you should also compare their outline, length-to-width ratio, face-up size, and brightness and scintillation under similar lighting. Two diamonds with similar grades do not necessarily have a well-matched appearance as a pair.
Are lab-grown diamonds the same as diamond simulants?
No. Lab-grown diamonds and natural diamonds have different origins; simulants are other materials that look similar to diamonds. Before purchasing, confirm whether the diamond is natural or lab-grown, whether it has undergone any treatments, and which reports and product disclosures apply.
How can I start shopping for a diamond if I do not understand the 4Cs?
You can first provide the purpose, budget, preferred shape or style, and the date needed. You do not need to decide on all the 4Cs first; WILLS JEWELLERY can discuss purchasing directions based on your needs, while individual options and availability must be confirmed separately.
Where can I book a WILLS JEWELLERY diamond consultation in Hong Kong?
You can book an appointment at the WILLS JEWELLERY Central Private Showroom, located at Room 1003, 10/F, Tak Woo Building, 17-19 D'Aguilar Street, Central, Hong Kong (No. 1 Wo On Lane). Please book online or WhatsApp +852 3571 9629 in advance to confirm the time and the diamond or piece you would like to view.
You do not need to know all the 4Cs first,
Only then can you begin shopping.
Start with the jewelry you want to wear or give as a gift. Sharing your purpose, budget, and preferences is more helpful than forcing yourself to fill in a set of specifications you have not yet decided on.
- Share Your Needs: Purpose, budget, shape, or reference styles.
- Discuss Options: Clarify specifications, appearance, and feasible directions.
- Confirm Arrangements: Check availability, pricing, and viewing appointments.
Pricing and availability vary depending on the individual gemstone, setting, and market conditions. This page does not provide real-time quotes and does not guarantee that specified pieces are regularly stocked at the store.
Diamond Purchasing Consultation in Central, Hong Kong
Comparing size, light performance, and how the piece looks when worn in person can make the information in a report more tangible. You are welcome to book an appointment at the WILLS JEWELLERY Central Private Showroom.
Before your visit, please share the diamond or piece you would like to view so we can confirm availability and make arrangements in advance. Individual gemstones may not be stored at the designated store.
17-19 D'Aguilar Street, Central, Hong Kong
Room 1003, 10/F, Tak Woo Building
(No. 1 Wo On Lane)
Visits: Please make an appointment in advance
Phone / WhatsApp: +852 3571 9629
Gemological Information Sources and Notes
- GIA · Diamond Cut
- GIA · Diamond Carat Weight
- GIA · Diamond Color
- GIA · Diamond Clarity
- GIA · Report Check
- GIA · Blue Fluorescence and Diamond Appearance Research (PDF)
This page provides general educational and purchasing information. It is not a grading conclusion, valuation, or investment recommendation for any individual diamond. For the specifications, identity, treatments, reports, and availability of individual products, please refer to the actual product information and confirm the details with a jewelry consultant. Educational images should not be used as a basis for grading an actual stone.
Content provided by: WILLS JEWELLERY. GIA is an independent gemological organization; its information is cited on this page and does not constitute an endorsement of WILLS JEWELLERY by GIA.
