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  • Samantha May Lee

Understanding The Moissanite Grading Certificate

When buying a Moissanite - whether loose or already mounted on a ring or any type of jewelry - a grading certificate plays an important role to make an informed decision if the asking price is justified by the stone's quality.

It is always advisable to read the grading certificate of a precious stone you are buying whether it is lab-grown or mined. A grading certificate will tell you whether the seller's claim of the stone's quality has merit. Beware of companies who mine or grow their own stones and also print their own grading certificates. Most of the time, they will exaggerate the quality of the stones. It is also a good practice to make sure that the certificate was issued by a reputable company and verify its authenticity to validate the accuracy of the certificate. Due to the time that the stone needs to spend at the lab and the additional cost, not all Moissanite stones are accompanied by a grading certificate. But if you are investing a substantial amount on your engagement ring, it is advisable to request that the stone be graded by an independent laboratory.


The image above is an original scanned copy of PGGL's grading certificate of a Halley Reh Extra-Ordinary Loose stones. A Halley Reh loose stone is dubbed "extra-ordinary" when its size is above 3 carats and its grading falls within the "Excellent" ranking zone on all categories. In the above certificate, you will see that this particular stone met all the requirements.

To better understand the certificate's information, we've broken down all the parts and nitty-gritty details below for your reference. We are going to start from the upper left corner going to the right.


  1. Shape Cut - On the farthest left corner of the certificate, you will see the shape cut of the gem being graded. In this particular certificate, it is an oval-shaped Moissanite.

  2. Carat weight - Carat refers to the actual weight of the gemstone being graded. Carat is a unit of mass that is equivalent to a fifth of a gram. In a Moissanite grading certificate, you will always see two carat weight values--the actual weight of the Moissanite stone and its diamond equivalent weight or DEW. The diamond equivalent weight value is always greater because Moissanite is between 15 to 20% lighter than diamond. This means that for the same carat weight, a Moissanite will appear 15 to 20% bigger in size than a diamond. Gemstone prices are also based on its carat weight and as expected, it is an important determining factor of the gemstone's price.

  3. Certificate Number - This is a unique number assigned by the company grading the gemstone. This information is important because this is the information that the grading company will need if you are to inquire about the certificate's authenticity and to validate its claims. We have blocked this information for our customer's privacy.

  4. Date - The date of the certificate is also important. The date will tell you when the stone was graded and it is ideal that the certificate is less than 5 years old when buying a new jewelry or loose stone and less than 2 years old if you are buying a used jewelry or loose stone because the quality of the stone may not be the same due to chipping and regular wear and tear. Sometimes, a seller of a used jewelry will demand a higher price sighting the stone is certified or the jewelry has a certificate of valuation, even though the certificate was issued 20 years ago. You cannot assume that the stone and the jewelry will be of the same quality after 20 years of use. You may request that the certificate be upgraded to reflect the current condition of the jewelry and its stone so you are not getting the jewelry's information when it was new two decades ago.

  5. Brilliancy and Profile Images - This information provides a form of security in making sure that the stone you are buying is the same stone on the certificate. The brilliancy image is the stone's actual image taken by the grading machine under ultra-violet light and the profile image provides the stone's actual measurements and proportions. It is very difficult if not impossible to have two stones with the same exact measurements and proportions as each stone is polished by hand.

  6. Light Grade - This information is the professional stone grader's observation of the stone's overall brilliance, sparkle and intensity when light passes through the stone and bounces back to its crown.

  7. Color - Moissanite's color is divided into Colorless (DEF), Near Colorless (GHI), Faint Yellow (KLM), Light Yellow (NOP), and Bright Yellow. As with diamonds, the absence of color in clear Moissanite (usually gray or yellow), especially above 2-carats is rare and more expensive. However, to the untrained eye, there will be no visible differences between the colorless, near colorless, and faint yellow especially if the stone is mounted on yellow gold. G-H-I colorless can be perceived almost as clear and colorless as the DEF stones, but they are significantly less expensive per carat. GHI stones are far more in demand than DEF because of its practical value.

  8. Clarity - Even though all Moissanite used in jewelry are lab-grown, they do develop some inclusions just like naturally mined diamonds. Flawless (FL) and Internally Flawless (IF) Moissanite shows no inclusions or blemishes even when viewed under 30x magnification. Very Very Slightly Included (VVS1 and VVS2) shows inclusions that are extremely difficult to see even under 30x magnification, and usually only visible from the pavilion, which is the stone's the lower part. Very Slightly Included (VS1 and VS2) means some inclusions are visible within 10x magnification but still very difficult for a technician to see. These inclusions will not be visible under the same magnification to anyone who is not an expert grader nor will it be visible to the naked eye. As with a diamond, a Moissanite's clarity grade has an enormous determining factor to its price.

  9. Polish- Polish refers to the condition of the stone's surface. This characteristic reflects the stone cutter's skill and is one of the determining factors of the stone's quality and price because a poorly polished stone will emit less sparkle and brilliance. The Moissanite's polish is graded on a scale consisting of excellent, very good, good, fair, and poor. Polish grades below ‘good", means that the brilliance of the stone is compromised and its poor sparkle is visible even to the untrained eye.

  10. Fluorescence - Fluorescence is the reaction of the Moissanite under an ultraviolet light that causes the stone to emit a sort of glow or halo if you will that detracts from the stone's appearance. Fluorescence is graded on a scale from None, Faint, Medium, Strong and Very Strong depending on the intensity. In intensities from Medium onward, the color of the Fluorescence will be noted in the report. In general, the less intense the Fluorescence, the more brilliance and sparkle the stone emits. Therefore, it is advisable to shy away from stones that have a fluorescence grade of more than Medium.

  11. Overall Symmetry - Symmetry refers to the Moissanite's overall shape and alignment. The grades for Moissanite's symmetry are the same as with the Polish grade. Any grade that is below "good" means that the stone's overall appearance is affected even without magnification.

  12. Girdle Thickness - A gemstone's outermost edge is known as the girdle. The girdle thickness is graded on a scale consisting of None, Small, Medium, Slightly large, Large, Very large, Extremely large. The ideal girdle thickness should not be too thin such that it causes a heightened risk of chipping nor should it be too thick that results in "dead weight" that makes the stone appear smaller. Moissanite with extreme girdle thickness variations such as very thin or extremely thick is an indication of symmetry disproportion and a poor cut that affects the stone's optical qualities and may also cause some problems during the stone's setting process.

  13. Measurements and Symmetry - The information on the table below this category reflects the measurements and proportion with reference to the stone's table, crown, girdle, pavilion, and culet. The table is the flat part on top of the stone facing up. 56.16% represents the percentage of the size of the table in relation to the outline shape of the whole Moissanite stone that is being graded. The girdle is that facet that goes around the diameter of the stone. It separates the top portion of the stone called the crown and the bottom part called the pavilion. Its thickness is measured as a percentage of the stone's diameter such as Thin (1.0%), Medium (3.0%), Thick (4.0%), and so on. The crown angles the axial symmetry and the pavilion angles are very important pieces of information because these greatly affects the visual appearance of the stone, the lower the depth percentage, the larger the stone will appear when looking at it facing up directly through the table.

  14. Culet Width -Culet is the facet or the tip at the end of the pavilion, opposite the table. If the pavilion facets are uniformly cut at the proper angle, it meets at a perfect point, resulting in no culet or a pointed culet. When the pavilion facets do not meet at a point, the culet becomes an additional facet to the stone's total number of facets such as with a round brilliant cut Moissanite with a faceted culet will have 58 facets, while a round brilliant cut Moissanite with a pointed culet will only have 57 facets. Large culets are not desirable by modern cutting standards because light can escape through it instead of bouncing back to the stone's crown. It is also visible when the stone is viewed from its table appearing as a dark circle. However, some cutters may intentionally cut a small culet since the absence of it, though more desirable, may result in a slight risk of chipping during the setting process or while being worn.

  15. Comments - Other observations by the stone grader will be noted in this section such as laser inscriptions or the color of the stone's fluorescence.

While it is important to understand the stone's grades in relation to one another, it is also important to realize that a stone may still look very appealing and still be drawn to its overall beauty and character even though it may have some slight imperfections. It is important to look at the stone's grades as a whole and not base your decision on just one element.


Grading Certificate is important to read and understand to make sure that you are buying a quality stone, but you must also remember that no one will go around with a loupe in their pocket and a grading machine in their car to ask if they could inspect your new engagement ring.

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