All diamond lab certificates are different in appearance, with similar information appearing in different formats. Here are photos of two of the diamond gem lab certificates for your inspection.

You will notice that they all look official, with a lot of information that you may not understand. Here are the basics to help you understand each piece of information that you will find on all the diamond certificates.

A G.I.A. Certificate, click here for larger image. An E.G.L. Certificate, click here for larger image.

Each certificate has the name of the laboratory which issued the certificate.

Each certificate has a certificate number. This number identifies your diamond, which the lab keeps a copy on file of all the data pertaining to your diamond. You can always call the lab that issued the certificate for your diamond for more information.

The shape and cutting style of the diamond, will indicate exactly what your diamond looks like. Round, Pear, Oval, Marquise, Heart, etc.

The measurements of the diamond. These numbers refer to the minimum and maximum width and depth of the diamond if it is a round diamond. A fancy shape diamond will have three measurements: length, width, and depth. These measurements are calculated using a micrometer which measures to the hundredth of a millimeter. This is a very good way to ensure that you always know your diamond: its millimeter size is unique to your diamond.

The weight of the diamond, is measured in Carats. You will see carats abbreviated with the letters “ct”. A carat is a unit of measure, which equals 0.20 grams and .007 avoirdupois ounces. There are 100 points to a carat. A three quarter carat is 75 points or .75ct, A half carat is 50 points, or .50ct.

Remember that carat weight does not necessarily relate to the diamond’s visual size. A diamond that weighs .75ct ideal cut will look the same visual size as a very deep cut 1.00ct diamond. There are approximately eighteen (18) different weight categories for diamonds, with different pricing for the different shapes. This combines to create seventy two (72) different combinations of shape and carat weight price categories.

The proportion section of the certificate tells us how well the diamond is cut. There are usually six pieces of information to make up the proportion section on most certificates.

The depth percentage is the percent of the depth of the diamond. It is determined by dividing the total depth of the diamond (from table to culet) measured in millimeters, by the average width of the diamond.

The table percentage is the percent of the table in relation to the width of the diamond. It is determined by measuring the width of the table in millimeters and dividing the table width by the average diameter width of the diamond.

The girdle is the outside edge of the diamond, where the top of the diamond (the crown) meets the bottom of the diamond (the pavilion). The girdle can vary in thickness, so it is described as a range. There are two methods of description: the plain English terminology that uses terms from extremely thin to extremely thick and percentage numbers that appear like .015% to .190%.

Culet is the very bottom pointed tip of the diamond, where the pavilion facets meet. A diamond can have no culet, very small, small, medium, etc.

The finish section includes the polish and symmetry of the diamond. The polish refers to the quality of the polish on the facets of the diamond. It is rated from excellent to poor. The symmetry of the diamond refers to how the diamond is shaped, if the culet is directly in the center line of the diamond, if the top facets line up with the bottom facets, if the diamond is round, is it perfectly round within 100th of a millimeter, or is it out of round visually?

The clarity grade is a description of any inclusions that might be inside the diamond. It is based upon viewing a diamond from the top with a ten power magnifying glass called a loupe. Any inclusions must be visible with the ten power magnifying glass to be graded. The laboratory has trained the gemologist grader by the standards of that particular lab. Each gem lab has different grading standards by which the graders judge the clarity of the diamond. This means that each lab certificate clarity grade is slightly different from lab to lab.

The color grade of the diamond is a description of the body color of the diamond. D was selected by the GIA in the 1930’s as the highest color a diamond can attain. The AGS lab uses a color scale based on a number system. 0 is the highest color, ranging to 9. There are divisions of the number system that relate to the GIA system.

Fluorescence is a description of a diamond’s appearance when exposed to long wave ultra-violet light. Sunlight has LV light as part of its spectrum, while a black light bulb emits LV light that is not visible to the eye. The fluorescence of a diamond can vary from none to very strong. Each combination of diamond body color and fluorescence has a visible description and value. Some combinations are more attractive and appealing than other combinations.

All these details that appear on a diamond lab certificate describes the beauty or lack of beauty of a diamond. It is very important for you to grasp the significance of what these details really mean. Now can you judge the importance of each piece of information on the certificate, understand what each piece of information really means, then how to price each piece of information, then integrate all the different pieces of information to determine a price.