Jewelry Blog

Understanding your UGL Certificate

UGL Engagement Ring Appraisal Report on table

Many jewelry and gemstone appraisal agencies operate in the US today. The Universal Gemological Laboratory (UGL) is considered one of the leading companies. There are many reasons to get a UGL Certificate, but the most common two are to verify jewelry before purchase and to get jewelry insured.

What is a UGL Certification?

A UGL certificate is an appraisal document generated by the UGL that provides certified information on a jewelry item or gemstone. Unlike the GIA, which will only give direct information on a specific gemstone, UGL certificates are designed to assess and grade an entire piece of jewelry with all the gemstones. Additionally, the UGL will certify gemstones without requiring them to be removed from their original jewelry setting.

Guide to UGL Jewelry Appraisal

Here is an example of a standard UGL certification:

UGL Certificate Example

A UGL Jewelry Appraisal is intended as a valuation guide for a piece of jewelry.

An appraisal itself is broken down into four areas.

  • Main Description. This will usually include a few lines describing the primary jewelry item.
  • Secondary Description. This will usually include a few lines describing secondary gemstones and information about the accenting elements of the jewelry piece.
  • Comments. This area will contain important information about the appraisal experience and disclaimers or matters the appraiser was uncertain about.
  • Value. The value is usually for insurance and presents the cost of remaking the jewelry.

Additionally, an image taken at the time of valuation will be on the right-hand side of the printed report. The above example is of a diamond engagement ring. If the ring has features essential to the overall identification, more than one image will usually be included.

    On the left side, the report begins with an appraisal date and the unique certificate number.

    Main Description of the UGL Certificate

    UGL Certificate Description

    The bulk of the report is taken up by a broad description of the item. It will contain a more detailed appraisal of the diamond(s) used in the ring. If more than one diamond (or other stone) is present, these, in turn, will be appraised separately. They will be distinguished by an alphabetic prefix – a), b), etc.

    Our example shows a Lady’s Engagement Ring with a round brilliant-cut diamond. The diamond is 0.40 carats, and its measurements of 4.80mm—4.75mm indicate its actual roundness. Ideally, these would be the same, indicating a perfectly round diamond. Practically, even with the latest techniques, it is rare to see this measurement without a minor difference.

    The clarity is VS1 Clarity, which indicates the diamond is “very slightly included” when viewed at a 10x magnification. The gradings for clarity range from Flawless to Included 3. A VS1 diamond will include flaws and blemishes that can be seen with 10x magnification. However, they will be difficult for the naked eye to see.

    The color given is H Color. The colors range from D (colorless) to Z (light yellow). An H color means that this particular diamond is considered nearly colorless.

    Secondary Description of UGL Certificate

    UGL Certificate Secondary Description

    The Secondary Description will be the section where the gemologist will provide more details about the ring/stones.

    In the image, it is clear that more diamonds are present in the setting. These are appraised separately from the central stone using the same grading scales. Each additional element will need its carat weight, clarity, color, and cut.

    This section ends with a general appraisal of the polish and symmetry of the diamonds. It will also often end with an overall gram-weight of the jewelry item.

    Comments Section of the UGL

    Comments on UGL Appraisal

    Companies like UGL don’t remove the diamond from a ring when giving it an appraisal. The appraiser can only offer an opinion on what can be seen.

    The phrase “Grading As Mounting Permits” is included. This disclaimer says that the diamond hasn’t been inspected to the same standard as a loose stone.

    This section also indicates the valuation is intended for insurance purposes. Insurance valuations are not used to value a piece for sale, as the resale and replacement values may differ.

    Additionally, this section may contain notes the appraiser was uncertain about, such as the gemstone’s origin, carat size, or whether it is natural or lab-grown.

    Value Section of the UGL Certificate

    Estatimated Retail Value on Appraisal

    The value section of the UGL report is usually the most important part of the document. It will include what is called an “Estimated Retail Value” amount. This amount is not how much the retailer charged. The estimated retail value is usually the price that the appraiser believes will be required to replace the jewelry item at today’s current jewelry market prices.

    The estimated value will usually be slightly more than the purchase amount, but not always. Additionally, if the customer gets a good deal from the retailer or the market prices are lifted, the estimated retail value can be significantly larger than the customer’s pay.

    Holograph Seal and Signature

    Holographic Seal UGL

    The certificate is completed by including the official UGL holograph seal.

    The appraiser’s signature and printed name are also on the document. In our example, Robert A. Lejman has the letters G.G. (GIA) after his name. G.G. indicates that he is a Graduate Gemologist from the Gemological Institute of America.

    The UGL Diamond Certificate

    Here is an example of a UGL diamond certificate.

    Complete Copy of a UGL certificate for diamond

    The UGL Diamond Report is split into two sides. On the left is the actual grading for each of the Four Cs, together with specific size information and a few other details. On the right are the scales used in the clarity and cut sections of the appraisal, together with a picture of the actual diamond. The scales are those used throughout the industry, and so they will be understood by anybody with experience in diamond grades.

    The certificate will always contain the date that the report was compiled, followed by the physically measurable qualities of the diamond.

    Shape and Cut

    Almost all diamonds are cut into one of several recognizable shapes known by unique names. In this case, the cut is the Round Brilliant, the most popular diamond cut today. Because the Round Brilliant cut has specific requirements for the number of facets, together with the measurement of the proportions of the cut stone (table, crown, and pavilion), these aren’t explicitly mentioned in the report. It is assumed that simply having the type of cut on there is sufficient for dealers and jewelry makers to know what it should look like.

    Learn more about a diamond’s shape and cut.


    This will always be comprised of 2 specific measurements. The first is always the smallest-largest measurement. In the case of a Round Brilliant cut, this indicates how round the polished stone actually is. The wider the gap between the two, the less round it is, with the ultimate aim being identical numbers on either side of the divider.

    The other measurement is the overall height of the diamond from the table to the culet. All dimensions are given in millimeters, allowing for much more accurate measurements than if inches were used.

    Carat Weight

    The other measurable aspect of a diamond is its weight. Diamonds are always weighed in carats, an ancient measure based on fine grains of the Carob plant. One full carat equals 200 milligrams, or 0.2 grams, and is always stated as a decimal (for example, 1.5 carats equals 300mg). Technically, the carat is a measure of mass and not weight, but it is universally adopted as the unit of measurement for precious metals and stones.

    Learn more about diamond carat weight.


    The proportions of a cut diamond are very important, as these give a great deal of insight into the likely light-reflective and refractive properties of the stone. They can also affect the “carat look” of the stone. The proportions are technical, but you can usually use each item from the list to determine the quality of the diamond’s proportions.

    Depth: The depth is a simple calculation of a diamond’s depth (height) by the width. The ideal depth is considered to be somewhere between 59.5% and 62.9%.

    Table: The table is the flat part of the diamond at the very top. A Round Brilliant cut is measured as a percentage of the overall width of the diamond. Ideal proportions are somewhere between 54% and 60%.

    Girdle: The girdle is the thin line around the perimeter of the diamond. It marks where the crown meets the pavilion. The girdle is measured as a percentage of the overall size of the diamond. It is always stated in base terms as very thin to extremely thick. A girdle that is too thin will leave the edges susceptible to damage. A girdle that is too thick is considered displeasing from an aesthetic viewpoint. The ideal girdle is medium.

    Culet: The culet is the very bottom of the diamond, which may have been cut to a small flat area or polished to a perfect point. These can range from none to extremely large. No culet is ideal, but extra care must be taken when setting the stone, as the point is quite fragile. A Medium culet offers extra protection against damage but may affect the stone visually.

    Diamond Color

    The color of a polished diamond is the most subjective part of any appraisal. Although most experienced appraisers will have very similar opinions of which color grade is appropriate, they differ. The color is graded from D, which signifies colorless, to Z, which will have a marked yellow tint. Past this point, or for diamonds of other colors, they will be called fancy diamonds. Learn more about diamond color.

    Diamond Clarity

    The clarity of a diamond determines how many flaws or inclusions can be seen when using a 10x loupe to examine the stone. The scale goes from flawless to included. There is also an Internally Flawless grading, which acknowledges that the diamond itself is flawless but that there may be minor polishing or other marks on the surface. Flawless is the ideal clarity. Learn more about diamond clarity and inclusions.


    Finish is an assessment of the overall appearance of the diamond, considering the shape (symmetry) and the quality of the polish. It is based on the gradings laid out above in the report.


    When viewed under ultraviolet (black) light, some diamonds emit a slight blue glow. This is caused by the presence of boron in the diamond’s structure and can be either an advantage or disadvantage, depending on the grade of the diamond.

    In colorless diamonds (grades D-F), any fluorescence will detract from the diamond and may affect its value by up to 15%. This is despite the accepted fact that almost nobody will see the difference in any natural light situation.

    With diamonds containing some hint of yellow, fluorescence can help, as the blue helps to cancel out the yellow, making a visibly less colored diamond. This can occur even in natural light, so fluorescence is a definite advantage for many lower-quality stones.

    Other Information

    UGL also offers the option of a dollar value grading on their certificates. Whether this is useful or not is questionable. The value shown will only be appropriate at the time of the appraisal.

    Like any traded commodity, the diamond market is subject to fluctuation. The dollar value given by UGL may give a misleading impression of its actual value at the time of sale.

    Talk to an Expert

    Do you have any jewelry-related questions? Feel free to send us a message using the form below.


    About Benjamin Khordipour

    Benjamin Khordipour is one of the jewelry researchers and gemologists at Estate Diamond Jewelry. He received his official gemological degrees from both the GIA and GUBELIN. He also regularly contributes to Business Insider, Forbes, Rapaport, CNBC, and Brides Magazine. Benjamin was born in New York and joined Estate Diamond Jewelry in 2014. He is passionate about vintage jewelry and diamonds. This blog was built on his strong belief that jewelers have a responsibility to properly educate their customers. In 2019, Benjamin co-authored the book The Engagement Ring Guide for Men. His favorite vintage jewelry era is the Art Deco Era and his favorite type of stone is the Kashmir Sapphire. He also collects rare antique pins.