Glossary of Terms

ImaGem Gem Grading Certificate provides superior information for round and fancy cut diamonds, gemstones and jewels based on patented direct measurement technology licensed to ImaGem, Inc. a U.S. Corporation.

Shape, table and girdle alignment, symmetry, color, fluorescence and light behavior are measured with unparalleled accuracy and described in clear and concise manner on the certificate. This is a truly discriminating document relied upon by consumers and jewelers for buying and selling gems.

No other grading certificate, foreign or domestic, comes close to providing so many exclusive features as are included in the ImaGem Certificate. Following is a brief description of this certificate.

Profile Image: The Profile image is drawn to scale to show exact relationship between table, girdle, pavilion, crown, and girdle thickness. Depending on the cut, the Profile Image shows up to three crown and three pavilion angles - an exclusive offering from ImaGem.

Brilliancy Image: This image illustrates the actual light behavior of your gemstone to reveal its beauty. White areas in the brilliancy image are the brightest; a lighter shade of blue represents more light return than a darker shade. Other colors represent lower amounts of light behavior. Brilliancy Image shows the magnitude and the pattern of light return unique to your gemstone. 

Brilliance: Brilliance is one of three measures of light behavior of a gem. Brilliance is measured as the average light return within the girdle in the face-up position.

Sparkle: Sparkle is used to measure scintillation in a gem. Higher the sparkle value, higher will be the level of visual vibrancy of a gem.

Intensity: Intensity measures the brightest areas of a gem that give it a distinct pattern, such as the hearts and arrows. A beautiful gem shows a well-defined pattern of light and dark areas that is pleasing to the human eye. ImaGem is the only technology to measure the Intensity of light behavior in a gem.

Light Behavior Grade: The light behavior grade is highly recommended in selecting a beautiful gemstone. The light behavior grades are Excellent+, Excellent, Very Good +, Very Good, Good, Fair and Poor.

Color: Color grade is based on an independent measure of color by GL3200 Grading machine using patented technology. A gemologist reviews the machine grade and the gemstone before a final grade is assigned. ImaGem's color grade is guaranteed for repeatability within 1 grade.

Clarity: ImaGem uses patented technology to view and map features in a gem. We actually measure the number, the size and the location of flaws. A gemologist reviews the machine grade and the gem before a final grade is assigned.

Polish: Polish grade is based on a careful examination of a gem by a gemologist.

Symmetry: Symmetry is based on direct measurements of "Axial symmetry", "Table symmetry"' and "Girdle symmetry". Patents secured by ImaGem are used for these measures of symmetry and are available only on the ImaGem Grading Certificate.

Alignment: The girdle and table must be perfectly aligned in a well-made gem. Our alignment grade describes how well the table and the girdle are aligned to each other. Because of direct measurement technology it is now possible to measure this important feature of a gem accurately - another exclusive of this certificate.

Cut Grade: The cut grade is based on DFS technology developed by Mr. David Atlas and Dr. Lalit Aggarwal. It describes the craftsmanship and durability of a diamond based on the proportions of a diamond and its finish (polish and symmetry). It is a perfect compliment to light behavior. Do not confuse ImaGem's cut grade with cut grade from other labs.

Fluorescence: The fluorescence grade is based on actual measurement of fluorescence in a gem under a highly controlled lighting environment. This means you get a fluorescence grade which is accurate and reliable unlike a fluorescence grade from other gem grading laboratories based on a visual comparison to fluorescence in master stones under a non-standard lighting environment. Fluorescence grade is guaranteed for repeatability within 1 grade with 2 Sigma probability. 

Culet: A grade is assigned to culet to describe its size. Culet grade is used in DFS Cut grade system.

Measurements: All measurements except for the table have repeatability of plus or minus 5 microns for all size stones with 2 Sigma probability - highest in the industry.

Clarity Plots: Location and size of flaws is mapped using ImaGem's patented immersion technology. Mapping is further refined by a gemologist to prepare pavilion and crown views drawn to exact proportions.