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Today it’s increasingly vital to have a proper laboratory certificate for natural diamonds, lab grown (LGD) diamonds, and gemstones that one is considering buying. An independent laboratory document verifies the quality components affecting the gem’s value and salability. Not just any certificate will do, however. It must be from a top-notch grading laboratory that has earned its respect from both the public and the trade.
One of the leading diamond grading labs today is SGL (formerly Solitaire Gem Labs). Their expertise is international and highly regarded as the standard for excellence. These documents, also call diamond quality reports, are respected by the jewelry trade for their top notch inspections that accurately validates the quality of each stone.
The SGL Diamond Report
SGL has developed its own distinct diamond grading system for ranking natural diamond cut, color, and clarity. Today the lab grown diamond niche is so important to our industry, so SGL has likewise developed an accurate grading scale for these stones too. Because of the many details given on the diamond and LGD diamond report, understanding their system helps consumers grasp the language of the reports.
Characteristics Appearing on SGL Diamond Reports
Of the characteristics analyzed and recorded on an SGL diamond report, the following are vital to assessing a stone’s quality:
Measurements
This first task records an accurate measurement of the diamond's dimensions as measured in millimeters. The diameter of the stone, its crown depth, its girdle circumference, the pavilion depth are all meticulously recorded, so there is no discrepancy about the stone’s identity.
Style & Shape
This detail describes the stone’s shape, like round brilliant or emerald cut perhaps, and also records its cutting style. There are many modern cut styles especially with regard to round brilliant cut diamonds that have evolved over the years. Older cut styles like Old Miner, or Old European cut styles might also turn up in the lab. All these cutting styles help professionals to place the diamond in a certain time period too.
Proportion Factors
Today, cutting proportions are highly scientific. Using computer assisted technology, cutters can determine the exact proportions of each facet and their relationship to one another for the purpose of producing the highest brilliance. These factors which determine both the diamond's shape and proportions also consider weight on the stone. This is one of the top three factors used for determining its cut grade.
Cut Grade
A diamond’s cut grade goes from zero being the rarest and most desirable to ten, for the least desirable cut grade. Separate components contribute to forming a cut grade --- proportion, light performance, and finish.
Color Grade
A diamond’s color grade is always important. It becomes even more essential as a stone increases in size—because the color is more apparent in larger carat sizes. A grade of color, zero (D on GIA’s scale) being the most rare and desirable up to ten (Z also on GIA’s scale) having the least desirability. The scale can also indicate half points to better accommodate all the nuanced grades of color.
Clarity Grade
SGL gives a plotted diagram indicating inclusion types and locations on the stone. With absolute pristine transparency the stone handles light better. Completely Flawless stones however are exceedingly rare, and their value illustrates that. A clarity grade ranking of, zero (FL/IF—in GIA’s system) indicates the rarest and desirable clarity, with ten (or GIA’s I3) denoting the least desirable.
Carat Weight
Who doesn’t want the biggest diamond they can afford? We have learned to admire the large sized celebrity diamonds, and it’s given all of us an appetite for large carat weight diamonds. A diamond is measured by its weight (not size) going to the third decimal place.
Nature of Origin
Now more than anytime, owners are interested in their stone’s origin. Not only does it place the stone in a particular location, but it helps the stone’s owner understand the geo-political implications of their gem and affirm the uniqueness of their jewel.
Proportion Diagram
It is common to plot the stone being examined. This is one way to further exhibit the uniqueness of the stone being examined. The proportion diamond maps out the stone's actual proportions. A graphic representation of the stone’s dimensions help the owner to better understand the stone.
Understanding terms on a Diamond Quality Document
Depth
The height of a gemstone measured from its culet to the table when viewed from the side.
Table
Located at the center top of the diamond, the table is often the largest facet on a diamond.
Girdle
Around the circumference of a stone, the girdle is the part between the crown (top) and the pavilion. (underside). It may vary in thickness.
Culet
A polished center point, or minute facet along the center pavilion side (underside) of a diamond or other gemstone.
While this tutorial gives one a better understanding of what to expect on an SGL quality document, your diamond professional will be happy to offer additional explanations for any detail appearing on the report. This way, every shopper is an informed consumer - buying with confidence and knowledge.
SGL’s services are so thorough that many retailers rely on their expertise and the breadth of services offered. Things like laser inscription on the girdles of stones, and even diamond sealing (a type of packaging to assure customers of the authenticity of the stone) are but some of the advanced options that make this laboratory a stand-out facility.
SGL for Lab Grown Diamonds
SGL Labs is a leading provider of lab grown diamond certification services as well, providing comprehensive analysis of LGDs, including their origin, quality, and authenticity. So the lab grown diamond report contains the stone’s 4Cs - carat weight, color, clarity, and cut.
Importantly, the SGL lab grown diamond certificate provides information on the stone’s origin along with a plotting diagram of the stone’s physical characteristics, both internal and external.
Other Grading Labs in our Trade
GIA (Gemological Institute of America): pioneered gem and diamond education. They also developed the universally understood diamond grading lexicon known as the 4Cs.
AGS (American Gem Society): known for its detailed cut grading. While reliable, they are said to be slightly less strict on color and clarity grades than GIA.
EGL (European Gemological Laboratory): Acknowledged for strict grading and attention to detail.
IGI (International Gemological Institute): Said to balance strictness and affordability.
SGL may be the most sought-after laboratory for its impartial analytical expertise -including natural diamonds to LGD and gemstones both natural and created. Their reliability has made them the go-to lab for both natural and lab grown diamonds.
