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Diamond Education

Diamond Quality

Quality and value for the money are more important now than they have ever been when it comes to the important things we buy. A diamond is one of the largest purchases most people make, behind a home and automobile. Just as with any major purchase, you must understand exactly what you are purchasing, and what makes diamonds that may appear similar, have vastly different values.

The Gemological Institute of America (GIA) has established a system for grading diamonds, commonly known as the four c's. This system, when used accurately and completely, is the best way to assure the quality and value of a diamond. It is worth noting that this system can only be accurately applied when the diamond is loose, thus the reason behind McGivern Diamonds policy of only selling loose diamonds.

It is possible to send a diamond in to the GIA, and they will grade the diamond. This is what is referred to as a GIA certified diamond. GIA is the industry standard throughout the world for grading accuracy. They are an education lab, with no interest on where, or even if you purchase a diamond. This is the best assurance of accuracy that exists. A diamond with a GIA grading report, or GIA certified diamond, is the highest standard. These are all 100% natural diamonds, and have not been treated or enhanced in any way.

There are many other grading systems that are used to represent diamond quality. However, it is the GIA system that is recognized in the diamond industry. The GIA is a non-profit organization that has no interest where you purchase your stone. Unfortunately, too many other so called "independent" labs are for profit, with the jeweler's best interests in mind, not the consumers.

The Four C's

Carat Weight

Carat is actually a measurement of weight, NOT size. However, it should be relative to size. One carat is divided into 100 points. Two diamonds of equal quality can have vastly different values depending on their cut, color and clarity. This is illustrated in the two diamonds below.

Carat weight is the easiest of the four c's to determine, however the diamond MUST be loose. Too many jewelers approximate carat weight, for instance, when you buy a 1/2 carat diamond, which you assume to be 50 points, you may actually be getting less than that. Many store sell as low as 45 points, and represent is as "approximately" a 1/2 carat. There is nothing wrong with buying a "light" 1/2 carat, however the cost is significantly less. You should know that is what you are buying, and pay accordingly.

Ideal Diamond Cut

Cut Grading System for Round Diamonds

In January of 2006, cut grading for round diamonds was taken to a whole new level, as this is when GIA introduced their cut grade system for round diamonds. They have taken an entirely different approach to grading cut then virtually anyone else in the industry previously. Many diamonds rated as Ideal in the industry by past standards are given lower cut grades by GIA. Conversely, many past lower cut grades are regarded higher by GIA. This new system has proven to be the industry standard, and has been called the most accurate and comprehensive system for cut grade the industry has ever seen. We have listed details on both the GIA Cut Grade System, as well as the EGL cut grade system, which is similar.

GIA Cut Grade System for Round Diamonds

According to GIA, they have calculated the cut results for 38.5 million proportion sets based on the assessment of seven components. The first three Brightness, Fire, and Scintillation are appearance-based aspects. The remaining four Weight Ratio, Durability, Polish, and Symmetry are related to a diamond's design and craftsmanship. In the GIA Diamond Cut Grading System, each component was assessed individually, taking into account the relative importance of that component in the overall cut quality of a round brilliant diamond, and the ability of an average, experienced observer to consistently see the differences in cut quality based on these components.

GIA had been studying diamond cut for decades, when in 1989 the Institute turned a significant corner. It was at this time that new advances in computer technology allowed GIA researchers to analyze aspects of the appearance of round brilliant cut diamonds that once had been impractical and difficult to explore.

Using advanced computer modeling, we were able to replicate the way light behaves within a round brilliant cut diamond so that we could predict how a diamond would perform with regard to brightness and fire. To study these two aspects of face-up appearance, we analyzed tens of thousands of proportion sets. These proportion sets included: table size, crown angle, pavilion angle, star length, lower-half length, girdle thickness, culet size, and total depth. We also studied the effects of polish and symmetry. We found that all of these parameters were interrelated in their effects on light performance, and that no single proportion, or subset of proportions, could be considered alone. In addition, we found that there was a wide range of proportions that had the potential for high quality light performance.

For more detailed information, you can go to the GIA website.

GIA grades the cuts of Round Brilliant cut diamonds as follows:

  • Excellent
  • Very Good
  • Good
  • Fair
  • Poor

McGiverns recommends GOOD or better Cut based on this system. If you are really more quality driven, stick with VERY GOOD or better. If you are the ultimate perfectionist, then EXCELLENT cut grade may be the way to go.

Diamond Anatomy

EGL Cut Grade Ratings

  • Ultra Ideal
  • Ideal
  • Premium
  • Good
  • Fair
  • Poor

McGiverns has always recommended PREMIUM or better based on this system.

Cut Grading System for Fancy Shape Diamonds

Just as with rounds, Quality of cut is the most important factor in determining how well a fancy shape diamond will sparkle. The two prime factors in assessing quality of cut is depth and table. Depth is the depth of the diamond by width for fancies. Table is the large flat surface on the top of the diamond. Table is the table width divided by stone width.

The numbers listed below are just guidelines for ideal cuts, or what you should look for in these numbers as you scan our database. On fancy shapes, we base our grades on a combination of systems and factors which we feel are the most accurate in presenting ideal cut guidelines.

Keep in mind on the fancy cuts, brilliance is achieved through the interaction between depth, table, and length to width ratio. For example, two pear shapes, both with identical depth and table could look remarkable different depending on length to width ratio. There is no magic formula to determine brilliance, only general guidelines. Again, we are always happy to assist in finding the diamond with the most sparkle.

McGivern recommends PREMIUM cut or better.


  • Ultra Ideal: Depth 64.0-75.0, Table 62-69, Polish & Symmetry Very Good or Excellent
  • Ideal: Depth 64.0-75.0, Table 62-74
  • Premium: Depth 64.0-78.0, Table 60-77
  • Good: Depth 58.0-80.0, Table 58-82
  • Average: Depth 56.1-84.0, Table 53-85
  • Fair: Depth < 57 or > 84, Table < 51 or > 85

Emerald & Radiant

  • Ultra Ideal: Depth 63.1-69.9, Table 62-69, Polish & Symmetry Very Good or Excellent
  • Ideal: Depth 62.0-74.9, Table 62-72
  • Premium: Depth 61.0-76.0, Table 60-75
  • Good: Depth 58.0-80.0, Table 58-79
  • Average: Depth 56.1-84.0, Table 53-85
  • Fair: Depth < 56.1 or > 84.0, Table < 53 or > 85


  • Ultra Ideal: Depth 63.1-69.9, Table 55-64, Polish & Symmetry Very Good or Excellent
  • Ideal: Depth 62.0-73.9, Table 53-69
  • Premium: Depth 61.0-76.0, Table 52-75
  • Good: Depth 60.0-80.0, Table 51-79
  • Average: Depth 56.1-84.0, Table 50-85
  • Fair: Depth < 56.1 or > 84.0, Table < 53 or > 85

Marquise, Oval & Pear

  • Ultra Ideal: Depth 59.0-63.0, Table 57-60, Polish & Symmetry Very Good or Excellent
  • Ideal: Depth 59.0-63.0, Table 57-60
  • Premium: Depth 57.1-66.0, Table 53-63
  • Good: Depth 56.1-68.9, Table 52-66
  • Average: Depth 46.1-71.0, Table 51-69
  • Fair: Depth < 46.1 or > 71.0, Table < 51 or > 69


  • Ultra Ideal: Depth 63.0-69.9, Table 57-67, Polish & Symmetry Very Good or Excellent
  • Ideal: Depth 62.0-72.0, Table 55-69
  • Premium: Depth 60.0-74.0, Table 53-73
  • Good: 58.0-77.0, Table 52-75
  • Average: Depth 55.0-79.0, Table 51-79
  • Fair: Depth < 55.0 or > 79.0, Table < 51 or > 79

Heart, Trillion & Others

  • No industry guidelines for ideal cut

Other factors on a GIA Certificate the buyer needs to be aware of are the following:

Girdle: The outer edge of the diamond, or the widest point where the top meets the bottom, generally this will take care of itself if depth is correct. There is really no such thing as a perfect girdle, but there are certain ratings we recommend avoiding. We recommend against Extremely Thin or Extremely Thick.

  • F = Faceted
  • ET or XT or XN = Extremely Thin
  • VT or VN = Very Thin
  • T or Th or N = Thin
  • ST or SLT = Slightly Thin
  • M = Medium
  • SK = Slightly Thick
  • K = Thick
  • VK = Very Thick
  • EK = Extremely Thick

Culet: The bottom, or point of the diamond. Ideally this should be None to Small.

  • N = None
  • VS = Very Small
  • S = Small
  • M = Medium
  • L = Large

Polish & Symmetry: Generally minor cutting details of the stone, should be Good or better for both.

  • P = Poor
  • F = Fair
  • G = Good
  • VG = Very Good
  • EX = Excellent

Diamond Color

Diamonds come naturally in almost every color of the rainbow, however most people are concerned with diamonds in the white range. Along with cut, this "C" is also very important in determining the overall beauty of the diamond. Color starts with the letter D, being the whitest, or best, and goes down the letter Z, being more yellowish. It is the lack of color, or whiteness in a diamond that allows the light to pass effortlessly through the stone and disperse that beauty back to the observer. Color is not so much white versus yellow, as the chart tends to indicate, it is more light versus dark. A white diamond will look very clean, crisp, and brilliant, with a lot of pizzazz. A yellow diamond will not really look yellow, as it will look darker and dirty, without nearly the same brilliance. These are differences that you can clearly see, as you do not need to be a gemologist to see these differences.

About Diamonds: Diamond Color Chart

Fancy Yellow

McGivern Diamonds specializes in Fancy Yellow diamonds. These are diamonds on the other side of Z. They are such a pure yellow, they are considered to be Fancy Colored by GIA. They come in four color grades.

Fancy Light Yellow - This is the lightest shade of Fancy Yellow. This is a very light lemon yellow color. In many lights it will be difficult to detect the yellow color, however in natural light it will be easily seen.

Fancy Yellow - This is the most popular grade sold, and is a nice pure yellow color. This will be clearly yellow in all lights, although it will still appear best in sunlight, and lighter in fluorescent light. This is what McGivern's normally recommends, and most people are very happy with this color.

Fancy Intense Yellow - This is darker, and if you want to insure that you see the pure yellow color, in all types of lights, and have it be a darker richer yellow, then this may be a good choice. It is a little deeper color than the Fancy Yellow, and if seeing the darker color is imperative, this may be the color grade for you.

Fancy Vivid Yellow - This is the darkest, deepest yellow, and due to rarity, is much more expensive. A Vivid will normally be double that of an Intense. This is only for the ultra perfectionist in color.

Diamond Clarity

Clarity refers to how many flaws, or inclusions, are in the diamond. In most cases, clarity has very little to do with the beauty of the diamonds, rather it effects how the diamond looks under the microscope. To determine a diamonds clarity grade, it must be examined loose, under 10x magnification by a gemologist. Whatever minute inclusions there may be make every diamond unique. These are nature's fingerprints and in most cases do not mar the diamond's beauty nor endanger in durability. Without high magnification, these flaws are invisible. However, the fewer inclusions, the rarer your diamond will be.

Generally, if a diamond is SI-1 or above, it is flawless to the naked eye (VS-2 for emerald, princess and radiant cuts). If there is even a tiny inclusion visible to the unaided eye, the stone is usually graded an SI-2 or I-1. It is extremely important to view the diamond loose for clarity grading, as it is very easy to set an I-1 diamond, and by concealing flaws in setting, make the diamond appear to be much better. There is nothing wrong with this, as long as this is represented accurately and you pay according.

About Diamonds: Diamond Clarity Chart

Diamond Grading - GIA vs. EGL

GIA and EGL are not the same on their grading standards. EGL's grading system looks similar, but is actually quite different. A good guideline is to subtract one clarity grade and three to four color grades from the EGL grade to get the true GIA grade. For example, we would expect an EGL VS-2 H to grade SI-1 K/L if sent to GIA. Nothing wrong with buying an EGL stone, as long as you understand this and pay accordingly. These are all 100% natural diamonds, and have not been treated or enhanced in any way.


Physical property of the diamond - how it appears under black UV light in a laboratory environment. In a high color diamond (D-F), fluorescence is a negative from a price perspective, ideally it should be None or Faint. In a lower color diamond, J or worse, fluorescence is a positive. Keep in mind, this is from a pricing point of view, and even though the market may view fluorescence as a negative, the simple fact is in normal lighting, in most cases fluorescence is not detectable, and does not detract from the beauty. According to GIA, "Fluorescence is a common phenomenon in diamond. GIA studies have shown that the strength of fluorescence has no widely noticeable effect on a colorless or near-colorless diamond's appearance. In fact, many prefer the appearance of diamonds that have medium to strong fluorescence. In very rare cases (fewer than 0.2% of the fluorescent diamonds submitted to GIA), some diamonds with extremely strong blue fluorescence may appear hazy or oily." We also encourage you to look at this documentation provided by the Gemological Institute Of America fluorescence information.

  • N = None
  • F = Faint
  • M or MB or MED = Medium
  • S or STR or SB = Strong
  • VS or VSB = Very Strong