Diamond Laboratory Process- Basic Functions and Procedures

Diamond Grading – The AGSL Way : Part Two

*The following article was written in collaboration with the American Gem Society Laboratories. Special thanks to Dennis Mette, Operations Director of AGSL, for his invaluable cooperation.

Many consumers are curious about the journey that a diamond takes in acquiring laboratory certification. We place great value on the report that specifies the diamond’s identity and grading of the 4Cs, but we seldom stop to think about what it takes to make it happen. When you actually break down the process you begin to understand the full value added by a grading report from a high quality lab.

In this article we will discuss take-in procedures and the preliminary tests to validate receipt of a diamond before it enters the grading environment, the ethical need for and process of “anonymizing” the diamond before grading, and the various aspects of grading that will be conducted before a report is issued. Different labs have different practices and we will be focusing specifically on those conducted at the American Gem Society Laboratories. In later installments in the series we will delve more deeply into individual grading practices at the lab.

Diamond Receiving Process

Before a diamond makes its way into the actual grading environment it is received and validated against the documents supplied by the client. The receiving process at the AGSL is conducted in a separate, secured area in the front of the lab. There, the diamond(s) in the package are compared against the packing slip and any obvious discrepancies are immediately noted and communication with the client is initiated, in case a mix-up has occurred on the client’s part.

If the diamond is received without issue it is entered into the database and a unique number is assigned to it. The diamond is then barcoded and labeled removing any information tying the diamond to a specific client. In this way the diamond enters the grading environment with complete anonymity. This important procedure ensures objective grading and prevents influence peddling that has resulted in cases of over-grading at other labs in the past.

Entering the Grading Process

After completing the receiving steps in preparation for grading, the diamond enters the main grading area and goes to a station equipped with several instruments where one operator performs a series of initial tests and measurements.

First, each diamond is weighed on a digital scale and any discrepancies outside normal instrumentation tolerances are noted and communicated, alerting the client to a possible mix-up on the client’s part.

Mettler Digital Scale
Mettler Digital Scale

The next step is to test the diamond with the DTC DiamondSure™ instrument used as an initial screen to distinguish between natural, simulated and synthetic diamonds. If the diamond tests positive for anything other than natural the client is notified before any further work is performed.


The diamond is then scanned using Sarin Technologies High Definition non-contact measuring device creating a 3D image of the diamond. The data from the measurements of every facet of the diamond is fed to the proprietary software program at the heart of the AGSL Cut Grade System resulting in a calculation of light performance.

Sarin HD non-contact measuring device
Sarin HD non-contact measuring device

Finally, the diamond is put on a Colorimeter machine in order to estimate a preliminary color grade.

Sarin Colorimeter
Sarin Colorimeter

Assessment by Trained Diamond Graders

Having been screened, measured and assigned a preliminary color grade the diamond then enters the realm of human grading. Color, clarity and cut grade aspects including polish and symmetry are assessed by professionally trained graders using a variety of tools and techniques. Each grader has completed the Gemological Institute of America (GIA) Diamonds and Diamond Grading courses. Many of the graders are GIA Graduate Gemologists, and/or AGS Certified Gemologists. The diamonds are graded by a number of graders as a quality assurance measure to ensure accuracy and consistency.

In the later installments of this series we will go into detail about each of these steps in the diamond grading process. We will also discuss interesting issues such as what happens when a diamond fails the preliminary screening for natural/untreated. And we will discuss client communications, additional services such as laser inscription, website report verification, the various document options available to the client, and of course the secure return of the diamond to the client.

*AGSL accepts diamond submissions only from the trade. As an individual interested in submitting a diamond for grading or other services, please refer to the American Gem Society website, www.americangemsociety.org or the AGSL website to locate a jeweler who may be able to assist you.

by Bryan Boyne, G.G.
Vice President
Whiteflash Inc.


See the other installments of this series:

Part One: Laboratory Graded Diamonds – What are the benefits for the consumer?

Part Three: AGS Laboratory – Color Grading of Diamonds

Part Four: AGS Laboratories – Clarity Grading of Diamonds

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