Diamond and other gemstone certificates: everything you need to know
Introduction: who is this article for and why is it important?
This article is intended for future buyers of diamonds and other gemstones, jewelers, and everyone who wants to understand how to identify a real, high-quality stone and what the differences are between various certificates. Here you will find answers to the most important questions: how to distinguish a real diamond from an imitation, how to read a certificate, what the differences are between GIA, HRD, IGI, EGL, and Lithuanian Assay Office certification, and what to look for when buying a gemstone. This information is particularly important because only by understanding the differences and importance of certificates will you be able to make a safe and informed decision regarding a gemstone acquisition.
This page discusses diamond certificates in detail, their importance, and the main differences between the most popular laboratories, so you will find all the necessary information about diamond authenticity and quality here.
What are gemstones and certificates?
Gemstones are natural minerals used in jewelry for their beauty and rarity. A certificate is an official document confirming the authenticity and quality of a gemstone according to established standards.
Diamond, ruby, sapphire, emerald – gemstone certificates
Gemstone certificates
Gemstones – such as diamonds, rubies, sapphires, or emeralds – have long been valued for their beauty, rarity, and enduring value. The diamond is also one of the most valuable gemstones and is often used in jewelry due to its exceptional properties. A diamond is a natural mineral composed of carbon atoms formed into a unique crystalline structure, which determines its exceptional hardness and brilliance. Along with rubies, sapphires, and emeralds, diamonds are classified among the most valuable gemstones in the world.
However, appearance alone is not enough – the value of diamonds is often related to their authenticity and quality, which is confirmed only by an official certificate according to international standards. A certificate provides objective information about the properties of the gemstone and protects the buyer from misleading information. In this article, we will discuss how diamonds are certified, why a certificate is extremely important, which laboratories are considered the most reliable, and how their assessment methodologies differ.
Next, we will discuss how diamonds are certified and which laboratories are the most reliable.
How to identify a quality diamond by its certificate?
When choosing a diamond or other gemstone, the most important aspects to pay attention to are:
- International certificates: The most reliable are considered GIA, HRD, IGI; I will also mention other laboratories: EGL, GCAL, DBIOD, GSI, SGL, AGS.
- Certificate number: Each certificate has a unique number that can be checked in the official laboratory database.
- Evaluation criteria: A diamond’s value depends on criteria such as color, clarity, carats, cut, symmetry, polish, proportions, and fluorescence.
- Transparency and detail: International certificates (GIA, HRD, IGI) provide very detailed information, including drawings, diagrams, and laser inscriptions.
- Lithuanian Assay Office certificate: Mandatory in Lithuania, but provides simplified information, often with a ±20% margin of error.
- Main differences between certificates: GIA is considered the strictest and most reliable, HRD is popular in Europe, IGI is often used for jewelry, diamonds, and lab-grown diamonds, EGL assessments can be more lenient, and the Lithuanian Assay Office applies CIBJO standards (CIBJO is an international gemstone assessment organization that sets standards for certification).
Tip: Always ask for a certificate, check its number, and pay attention to the evaluation criteria. If in doubt, consult with an independent jeweler or gemologist.
Certified diamonds
Certified diamonds are evaluated in independent international gemological laboratories, such as GIA, HRD, or IGI, and in Lithuania – at the Lithuanian Assay Office. The stone being certified is a diamond, therefore strict international standards apply to it. In these laboratories, diamond properties are determined according to four main criteria – color, clarity, carat weight, and cut quality. An official certificate confirms the diamond’s authenticity and allows for an objective assessment of its value in the international market.
GIA certificate – the gold standard
GIA (Gemological Institute of America) is one of the most authoritative gemological laboratories in the world. Its issued certificates are considered the most reliable because they define diamond color, clarity, shape, and carat weight with extreme precision. Due to these strict evaluation criteria, GIA-certified diamonds often have higher value in the market.
🔹 Check a GIA certificate – this is one of the safest ways to ensure diamond authenticity, as this laboratory evaluates stones according to the strictest international standards.
How to read a GIA certificate?
A GIA diamond certificate includes all the most important information:
- The date the diamond was certified.
- Certificate number with a laser inscription on the diamond’s girdle.
- Diamond shape and cutting style.
- Diamond dimensions.
- Weight in carats (1 carat = 0.20 g, therefore the term carat in grams is also important).
- Color classification from D to Z.
- Clarity evaluation.
- Cut grade (Excellent – Poor).
- Polish and symmetry.
- Fluorescence.
It is important to know that certain parameters specified in the certificate are essential for accurately determining the diamond’s quality and value.
Diamond shapes
A processed diamond can take various shapes, but only a round-shaped and specifically cut diamond is called a brilliant. A brilliant is distinguished precisely by its cutting method and shape – a classic brilliant has 57 facets that reflect light to the maximum. Brilliant shapes must meet strict quality criteria, so not all diamonds can be called brilliants. It is important to understand that all brilliants are diamonds, but not every diamond is a brilliant, and a brilliant is the result of a specific cut.
Besides the classic round shape, diamonds can be other popular shapes – oval, princess, emerald, pear, rectangular, or heart. Each shape has its own character and aesthetic properties, which determine a different play of light and the overall image of the stone. It is important to emphasize that despite the differences in shape, all these diamonds are variants of the same mineral – diamond.
However, the round-shaped brilliant remains the most popular choice to this day. The final shape is usually chosen based on personal taste, style, and the individual expectations of the buyer.
Diamond clarity assessment according to GIA
Diamond clarity is evaluated according to the number of internal and external inclusions and their visibility. The evaluation scale starts from FL (Flawless) and continues to I3 (Included). This criterion has a great influence on the diamond’s value, but no less important for the price and visual impression is the chosen diamond shape.
How to understand the clarity scale
The fewer inclusions and defects a diamond has, the higher its clarity rating and the greater its value. FL and IF grade diamonds are extremely rare, while I1–I3 usually have inclusions visible to the naked eye.
Diamond color scale according to GIA
Diamond color is evaluated on a scale from D (completely colorless) to Z (with a yellowish or brownish tint). The less color a stone has, the rarer and more valuable it is. It is important for buyers to understand that color is one of the four main 4C criteria directly influencing a diamond’s appearance and price.
How to understand the color scale
D grade diamonds are completely colorless and the most expensive. The further the letter is in the alphabet, the more yellowish or brown tint the stone has, and the cheaper it is.
GIA proportion and inclusion diagrams
Each GIA certificate provides detailed diagrams and drawings marking the stone’s inclusions, proportions, and other important technical parameters. Diagrams often indicate the arrangement of brilliant facets, their number, and symmetry – properties that directly determine the diamond’s brilliance. Such information allows for the precise recognition and identification of each diamond as a unique stone.
HRD certificate
HRD (Hoge Raad voor Diamant) is one of the most authoritative gemological laboratories in Belgium, widely used in the European market. It is considered a reliable alternative to GIA, and its certificates are provided in several languages and are internationally recognized. Because of this, HRD-certified diamonds are often chosen for white gold engagement rings.
🔹 Check an HRD certificate – a reliable way to evaluate diamond quality, especially in Europe where this laboratory is highly regarded. Mostly used in the European market.
IGI certificate
IGI (International Gemological Institute) is a widely recognized gemological laboratory that certifies both natural and lab-grown diamonds. For this reason, IGI certificates are especially popular among buyers interested in lab grown diamonds. The laboratory operates internationally, so its evaluations are easily recognized and understood worldwide.
🔹 IGI certificate check – a convenient way to evaluate the properties of both natural and laboratory diamonds according to international standards.
EGL certificate
EGL (European Gemological Laboratory) also provides diamond certificates and is known in the international market. However, this laboratory is often viewed critically due to less strict evaluation criteria – in some cases, its evaluations can differ from GIA standards. Despite this, EGL certificates are still widely encountered and used in both the US and European markets.
🔹 Check an EGL certificate – an opportunity to review diamond data, though it is recommended to evaluate them by comparing with the standards of stricter laboratories. More commonly found in the US and Europe.
Swiss laboratories for colored gemstones
For the assessment of rubies, sapphires, and emeralds, Swiss gemological laboratories are often chosen, as they specialize in colored gemstone analysis and provide extremely detailed information about their properties. It is important for buyers to know that GIA certificates are not issued for colored gemstones in all cases, making other international laboratories an important and reliable alternative.
🔹 Check an SSEF certificate – a Swiss laboratory especially valued for colored gemstones such as rubies, sapphires, or emeralds, as well as diamonds – how to choose the best and invest wisely.
Lithuanian Assay Office – a guarantee of reliability
In Lithuania, having international gemological certificates is not mandatory, but every natural diamond must be checked at the Lithuanian Assay Office. The assessment is performed according to CIBJO standards – this is an international organization in the gemstone and jewelry sector that sets common certification requirements. After the check, an official document is issued – the Lithuanian Assay Office certificate, confirming the diamond’s authenticity.
What does the Lithuanian Assay Office check?
The Lithuanian Assay Office usually evaluates gemstones that are already set, so they do not have the opportunity to inspect the stone from all sides in as much detail as is done in international gemological laboratories. For this reason, the certificate indicates a possible assessment margin of error, which can reach about ±20%.
Diamond color comparison: GIA vs Lithuanian Assay Office (CIBJO standard)
| GIA color grade | Description according to GIA | CIBJO assessment (used in the Lithuanian Assay Office) |
|---|---|---|
| D | Colorless (highest quality) | EW+ (Exceptional White +) |
| E | Colorless, barely perceptible tone | EW (Exceptional White) |
| F | Almost colorless | RW+ (Rare White +) |
| G | Almost colorless, barely yellowish tone | RW (Rare White) |
| H | Slightly yellowish tone, but still valued | W (White) |
| I | Noticeable yellowish tone | STW (Slightly Tinted White) |
| J | More clearly yellowish, but acceptable | STW (Slightly Tinted White) |
| K | Clearer yellowness | TW (Tinted White) |
| L | Noticeable yellowness, lower value | TW (Tinted White) |
| M–Z | Vivid yellowness or brownness | Often combined into broader groups (e.g., Tinted, M–R, S–Z) |
How to understand the color comparison
In this table, you can see how the GIA letter color scale corresponds to the CIBJO terms used in the Lithuanian Assay Office. Different systems can cause confusion, but they evaluate the same parameter – the color of the diamond.
✅ Important to know:
- GIA uses a letter scale (D–Z), while CIBJO uses terms (EW, RW, W, STW, TW).
- CIBJO classification is often less clear to the final buyer because it uses abbreviations that are not always intuitively understood.
- Due to these differences, it might seem to a client that their diamond is graded worse, when in reality it is just a different classification system.
Diamond clarity comparison: GIA vs Lithuanian Assay Office (CIBJO standard)
| GIA clarity grade | Description according to GIA | CIBJO assessment (used in the Lithuanian Assay Office) |
|---|---|---|
| FL (Flawless) | No inclusions or blemishes visible even at 10x magnification | LC (Loupe Clean) |
| IF (Internally Flawless) | No inclusions, only surface defects | LC (Loupe Clean) |
| VVS1 | Very, very minute inclusions, difficult to see | VVS1 |
| VVS2 | Very minute inclusions, slightly easier to see | VVS2 |
| VS1 | Minute inclusions, difficult to see at 10x magnification | VS1 |
| VS2 | Minute inclusions, easier to see at 10x magnification | VS2 |
| SI1 | Noticeable inclusions at 10x magnification, often invisible to the naked eye | SI1 |
| SI2 | Noticeable inclusions at 10x magnification, sometimes visible to the naked eye | SI2 |
| I1 | Inclusions visible to the naked eye, may affect brilliance | Piqué 1 (P1) |
| I2 | Many inclusions, strongly affects transparency | Piqué 2 (P2) |
| I3 | Very many inclusions, reduces the stone’s durability | Piqué 3 (P3) |
How to understand the clarity comparison
The table presents the equivalent of GIA and CIBJO clarity grades. Although the names differ, the same thing is evaluated – the quantity and visibility of inclusions. The Lithuanian Assay Office often applies a more conservative evaluation.
The Lithuanian Assay Office does not perform such a comprehensive evaluation of gemstones as international gemological laboratories, so their issued documents often do not provide data on diamond cut quality, symmetry, or polish. As a result, customers often have questions when comparing these documents with international certificates.
Comparison: international laboratories vs Lithuanian Assay Office
What criteria do international laboratories evaluate?
A comparison table clearly showing what criteria international laboratories (e.g., GIA, HRD, IGI) evaluate:
| Criterion | International laboratories (GIA, HRD, IGI) |
|---|---|
| Carats | Measured very precisely (up to 0.001 ct). |
| Color | Evaluated by letters from D to Z. |
| Hue | Recorded if the diamond has a yellowish, brown, or other tone. |
| Clarity | Evaluated by GIA scale: FL, IF, VVS1–2, VS1–2, SI1–2, I1–3. |
| Cut | Evaluation of proportion quality: Excellent, Very Good, Good, Fair, Poor. |
| Symmetry | Evaluated on a scale: Excellent, Very Good, Good, Fair, Poor |
| Polish | Evaluated on a scale: Excellent, Very Good, Good, Fair, Poor |
| Fluorescence | Recorded as: None, Faint, Medium, Strong, Very Strong (with color type). |
| Proportions | Provided in detail (table size %, depth %, crown angles, etc.). |
| Shape | Clearly indicated (Round, Oval, Princess, Emerald, etc.). |
| Laser inscription | Number marked on the stone’s girdle, indicated in the certificate. |
| Comments | May include notes on fractures, polish, fluorescence effect. |
What criteria does the Lithuanian Assay Office evaluate?
| Criterion | Lithuanian Assay Office (CIBJO) |
|---|---|
| Carats | Visible, but there can be a ±20% margin of error in documents. |
| Color | Evaluated according to the CIBJO system: EW, RW, W, STW, TW. |
| Hue | A general tone is often recorded (e.g., yellowish, brownish), without a precise scale. |
| Clarity | Evaluated according to CIBJO: LC, VVS, VS, SI, Piqué (P1–P3). |
| Cut | Not evaluated. |
| Symmetry | Not evaluated. |
| Polish | Not evaluated. |
| Fluorescence | Usually not specified unless obvious. |
| Proportions | Not provided. |
| Shape | Usually only described, e.g., “round” or “fancy shape or diamond”. |
| Laser inscription | If international exists, it is usually checked but not recorded. |
| Comments | Notes are usually minimal – only basic parameters. |
Explanation: These tables help to understand what information you will receive with an international certificate and what with a Lithuanian Assay Office document. International certificates provide a detailed technical analysis, while the Assay Office provides a simplified one, focused on consumer protection.
✅ What the buyer should know:
- International certificates provide very detailed information, making them the primary source for accurately determining a stone’s quality.
- The Lithuanian Assay Office provides a more simplified and stricter evaluation, which is oriented towards buyer protection, rather than a comprehensive aesthetic or technical analysis of the diamond.
- If a diamond has fluorescence or another visual effect, international certificates record it precisely, whereas the Assay Office does not.
- Therefore, if you buy a diamond with a GIA, HRD, IGI, etc. international certificate, you have much more detailed information than from an Assay Office document alone.
- It is recommended to have both documents – the international certificate and the Lithuanian Assay Office conclusion.
Evaluation margin of error
It is important to note that evaluations by the Lithuanian Assay Office allow for an up to 20% permissible margin of error, which is clearly stated in official documents. This means that parameters such as color or clarity may slightly differ from assessments provided by international laboratories, such as GIA.
Buyer protection in Lithuania
The activities of the Lithuanian Assay Office are focused on protecting consumer interests, so their evaluation methodology is primarily intended to ensure buyer rights. Due to the applied safeguards and more cautious evaluation, the data provided in the documents may sometimes appear stricter or more conservative, but this is exactly what helps ensure greater transparency and reliability.
Certificates in Lithuania – which are mandatory?
It is important to emphasize that mandatory testing in Lithuania applies not only to diamonds – rubies, sapphires, and emeralds must also be evaluated at the Lithuanian Assay Office. Meanwhile, certification is not mandatory for laboratory-grown diamonds.
Lab Grown Diamonds and their certification
Artificial diamonds should not be confused with laboratory-grown diamonds. A laboratory diamond is a real diamond created under laboratory conditions, whereas artificial stones are just diamond imitations, such as moissanite or cubic zirconia. Distinguishing these concepts is very important because certificates are issued specifically for laboratory diamonds, not imitations.
Laboratory diamonds (Lab Grown Diamonds) are real diamonds with identical chemical composition and properties as natural ones, but grown in a laboratory. Synthetic or imitation stones (e.g., moissanite, cubic zirconia) only visually resemble a diamond but do not have the same properties and are not certified according to diamond standards.
Frequently asked: brilliant or diamond? or what is the difference between a diamond and a brilliant?
Diamond and brilliant are often used interchangeably, but they are not actually complete synonyms. A diamond is a natural mineral, while a brilliant is just one specific form of diamond processing. This difference is important because it is the processing that determines how the stone will look and shine.
Only a diamond that is round-shaped and cut according to strict standards, with 57 or 58 facets, is called a brilliant. This cutting allows for maximum light reflection and gives the stone an exceptional brilliance. Only diamonds that meet these shape and cut criteria can be called brilliants – brilliant, brilliants, or diamond brilliants.
There are many other diamond shapes – oval, princess, emerald, pear, or heart – which differ in both the number of facets and the cutting technique. Although all brilliants are diamonds, not every diamond is a brilliant.
In short: the difference between a diamond and a brilliant lies only in the processing. This is why these terms are often used as synonyms in everyday speech, although their meanings differ from a gemological point of view.
1 carat of diamond and brilliant
A carat is a unit of measurement for the weight of gemstones, where one carat equals 0.20 grams. Therefore, the equivalent of a carat in grams is often used. It is important to mention that the price of 1 ct of a brilliant is usually higher than 1 ct of an uncut diamond, as a brilliant is a specifically cut stone given maximum brilliance and added value.
Not all diamonds are the same
It is important to understand that not every diamond is suitable for jewelry. Only high-quality stones meet certification requirements and are used in jewelry making, while the rest are mostly classified as industrial diamonds intended for technical purposes.
Gemstone certificates – ruby
Ruby is one of the most valuable and highly regarded gemstones. The certificate provides essential information about its color, origin, and possible treatment methods, making it extremely important in evaluating the stone’s authenticity. It is recommended not to purchase rubies without an official certificate.
Gemstone certificates – sapphire
A sapphire’s value is determined based on its color, clarity, and origin. Sapphires coming from Kashmir, Myanmar, and Sri Lanka are especially valued and considered the most luxurious. An official certificate allows for the confirmation of the stone’s authenticity and ensures that the sapphire is not artificially colored or otherwise impermissibly treated.
Gemstone certificates – emerald
Emeralds naturally possess inclusions, which are a characteristic of this gemstone. The certificate provides information about their quality, origin, and applied treatment methods, so it is extremely important when evaluating the stone. Without a certificate, it is difficult to objectively determine an emerald’s value.
Practical tips for the buyer
- Always ask for a certificate.
- Check the certificate number in the GIA, HRD, or IGI database.
- If in doubt, consult with a jeweler.
Comparison: Natural Diamond vs Lab Grown Diamond vs Artificial Stone
Main differences between diamond types
| Type | Origin and Composition | Is it a real diamond? | Certificate (GIA, HRD, IGI) | Price of 1 carat diamond* | Price of 1 carat brilliant* | Notes |
|---|---|---|---|---|---|---|
| Natural Diamond | Forms deep within the Earth over millions of years | Yes ✅ | Yes, mandatory international certificate | from €1500 and up | from €1800 and up | Rare, unique, considered an investment |
| Lab Grown Diamond | Grown in a laboratory by recreating natural processes | Yes ✅ | Yes, certified according to the same standards | from €400–1800 | from €500–1800 | More eco-friendly, budget-friendly |
| Artificial Diamond (imitation: moissanite, cubic zirconia, etc.) | Synthetic or glass crystals visually resembling a diamond | No ❌ | Certificates do not apply | from €50–200 | from €100–300 | Visually similar, but lacks diamond properties |
Explanation: In this table, you can clearly see the differences between natural, laboratory, and artificial diamonds – based on origin, composition, certification options, and price.
* The prices indicated are only indicative and may vary depending on the stone’s color, clarity, cut quality, and overall market fluctuations.
Diamonds, brilliants, rubies, sapphires, or emeralds – all these gemstones gain real value only when they are confirmed by certificates. International documents such as GIA, HRD, or IGI provide additional reliability, and the Lithuanian Assay Office ensures that every gemstone is presented to the market transparently and in compliance with established requirements.
Frequently Asked Questions (FAQ) about gemstone certificates
1. Why is a diamond certificate important?
A diamond certificate confirms the stone’s authenticity, its quality properties, and its value according to international gemological standards. Without an official document, a diamond’s price may be unclear, and the information provided may be misleading to both the buyer and the seller.
2. What is the difference between a diamond and a brilliant?
A diamond is a mineral of natural origin, while a brilliant is a round-shaped diamond specifically cut to have 57 or 58 facets. This cutting allows for the maximum disclosure of the stone’s brilliance, which is why a brilliant is considered one of the most aesthetic diamond forms.
3. Are lab-grown diamonds real diamonds?
Yes, laboratory-grown diamonds are real diamonds because their chemical composition, physical, and optical properties are identical to natural ones. The only difference is their origin: they are grown under controlled laboratory conditions rather than forming deep within the Earth.
4. What are artificial diamonds?
Artificial diamonds are diamond substitutes, such as cubic zirconia or moissanite. Although they may look similar to a diamond, their physical and optical properties differ, so both their value and price are significantly lower.
5. What is special about a GIA certificate?
A GIA (Gemological Institute of America) certificate is considered the international “gold standard.” This laboratory applies extremely strict evaluation criteria for color, clarity, carat weight, and cut, making GIA documents some of the most reliable for both buyers and jewelers.
6. Is an EGL certificate reliable?
EGL certificates are widely encountered in the market, but their evaluation methodology is considered more lenient than GIA. In some cases, color or clarity evaluations can differ by as much as 2–2.5 grades, so the price of such a diamond may seem more attractive, but its real value is often lower.
7. Who checks gemstones in Lithuania?
In Lithuania, four gemstones: diamonds, rubies, sapphires, and emeralds are mandatorily checked at the Lithuanian Assay Office. This institution ensures that gemstones entering the market meet the international evaluation standards set by CIBJO.
8. What does the Lithuanian Assay Office determine?
The Lithuanian Assay Office checks the authenticity of gemstones and determines their basic properties, but does not evaluate parameters such as diamond cut, symmetry, or polish quality. For this reason, a comprehensive stone evaluation is still best ensured by international gemological certificates.
9. Is a certificate mandatory for lab-grown diamonds?
In Lithuania, a certificate is not mandatory for laboratory-grown diamonds, but having one is highly recommended. An IGI or GIA document provides more transparency and helps to accurately determine the value of a laboratory diamond.
10. Are certificates necessary for rubies, sapphires, and emeralds?
Yes, certificates are especially important for colored gemstones. They help determine the origin and possible treatments of rubies, sapphires, or emeralds. The most reliable assessments of these stones are usually carried out in Swiss laboratories, such as SSEF, which is considered one of the most authoritative in the world.
