What Goes Into Grading A Diamond?

A few weeks ago, I had the pleasure of traveling out to California for a few weeks - mainly for some R&R before a busy holiday season, but also to complete the final part of my Graduate Diamond training through the Gemological Institute of America

I've been pursuing my gemologist degree for the two years, focusing on the diamond part of the degree first, as I handle a lot of diamonds through my engagement work and often take in customer's stones to reset. I found that it was was becoming increasingly important for me to identify and appraise diamonds as I was working more and more with them, so I enrolled in GIA's Graduate Diamonds program - first learning about how diamonds are formed and the process that they go through to come to the earth's surface, then about diamond mining and cutting, and also focusing on the 4 c's of diamonds that give them their value. The final part of the degree was taking a lab class where I learned how to properly grade stones, what sets clarity, color and cut grades, and how small things can make a big difference when it comes to a diamond's value. 

Before heading to GIA's campus for the week-long lab, I thought I had a pretty good understanding of what makes up the quality of a diamond and how to identify these characteristics, through my previous coursework and from handling so many customer's stones. Let's just say that I quickly realized I knew *very little* about what actually goes in to grading a stone, and gave me a new appreciation for the entire process and the diamond industry as a whole. 

The first day of the course was entirely about familiarizing ourselves with the GIA as an organization and their process for grading and taking stones, as well as the instruments used to grade diamonds - mainly a microscope and jeweler's loupe. A jeweler's loupe is a very common jewelry tool used for just about everything on the bench, and it is what determines the final grade of a diamond. Anything that can be spotted through the loupe at 10x magnification (inclusions, chips, etc) are noted and ultimately set the clarity of a stone. So although the microscope, which can zoom up to a much higher magnification, is great to look closer at characteristics of stones, if it can't be seen at 10x then it technically can't be counted as a clarity characteristic. Getting your eyes adjusted to the microscope is pretty rough, so lots of breaks were taken the first day. We also learned how seriously GIA takes the conditions that their graders are working under. If they are over tired, feeling sick, or even just having an off day, they're asked to go home. Since the grading ultimately comes down to a person's judgement call, anything that might hinder their ability to make those decisions (especially something that can affect their vision) is treated seriously.

The next several days, the class intensively went through each of the 4 c's - carat weight, color, clarity, and cut - thoroughly examining each one and really learning how to determine a grade for it. In case you've never purchased a diamond, or just need a refresher, here's what we dove into:

  • Carat weight is the most straight forward of the 4 - the stones are measured on a scale for accurate weight, and with most scales being digital these days there's little room for error in determining the weight.
  • Cut is not only the shape of the stone, but also the proportions and actual cuts and facets on the stone. In this section, we learned a series of measurements and proportions to figure out what would make an excellent cut stone versus one of a lesser grade. Although the GIA lab has most of this done through a machine for extremely accurate measurements, we were taught how to do this by hand for two reasons. First, most jewelers do not have access to the equipment that the GIA does, so we need to learn how to do these measurements and grades with tools that we do have. Second, after several days of looking at different stones, your eyes start to learn and identify sizes and proportions, and it becomes easier to make a call.
  • Color is the face-up color that you see in a diamond. This is determined using a set of stones called masterstones. These are determined by the GIA to be the perfect reflection of each color grade. Color is graded on a scale from D-Z. D-F is colorless, G-I is near colorless, J-M is slight color, and N-Z reflects light yellow to brown color. Any stone being graded is held against white paper and compared with these stones to determine the proper color. While this may sound easy, it is surprising how incredibly difficult it can be to make a call - especially when a stone appears to be in between two colors. It is also amazing how much your eyes can play tricks on you during the color grading process. 
  • Clarity refers to any inclusions (inside the stone) or blemishes (on the surface of a stone) found in a diamond. This is what we spent the most time focusing on, as there 

In addition to this, we also looked at stone factors including how well it reflects light, the sparkle seen in a diamond, the pattern in a diamond, and fluorescence in a stone (ultraviolet light that can sometimes affect how a stone appears). 

Throughout the week, went through hundreds of stones, ranging from extremely poor quality to nearly perfect, and worked on determining a final grade. At the end of the course, we were asked to grade several stones and had to be within a certain range of the official GIA report in order to pass. 

So, what does all of this information mean for me? Well to start, it has given me a much better understanding of how to properly evaluate a diamond. But more importantly, it has made me appreciate the need for independent jewelers like myself, especially when it comes to buying a diamond for a customer. With the rise of diamond sales on the internet, it can be easy to purchase a stone that looks good on paper without actually seeing it, only to be disappointed or confused by the actual appearance of the stone in-person. While this may not happen all of the time, i'm surprised by the number of customers I deal with who come to me thinking they had purchased a high quality stone online only to have misunderstood the report, or feel let down by the physical appearance of the diamond. While there is enough information out there for an average consumer to get a basic understanding of stone grades, there are a lot of nuances in diamonds that take years of practice and learning to understand. A high color grade and lower clarity grade may be a great stone to use as an engagement ring, just as the opposite may be more money but appear lower quality. While there is no right or wrong diamond to use for fine jewelry, there are things that jewelers who are well versed in this information can help to advise on to make sure a person is happy with their purchase. 

Next up for my full gemology degree, i'll be moving into learning more about colored stones. I'll need to identify nearly 1,000 colored stones over a two year period, as well as take two additional lab classes. Lots of work, but extremely exciting! Stay tuned for more updates on my GIA journey. In the meantime, if you have any questions about diamonds and gemstones, or want to work with me on a custom piece of jewelry, please feel free to contact me

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