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.
The simple fact is all jewelers cannot sell the same diamond for the best price, but they still must make it appear that way. Thus many
other certificates exist that are far from accurate, and it appears you are getting the same grade diamond, for much less money. In the end,
the real question is, just because some certificate states the diamond is a certain grade, will GIA agree? Most likely not, thus these other
certificates can be discounted quite substantially, depending on how inaccurate they are. Wherever you end up buying, stick with a GIA
certified stone, they are the industry standard.
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 been 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.
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.
Princess
-
Ideal:
Depth 64.0-75.0, Table 62-69, Polish & Symmetry Very Good or Excellent
-
Very Good:
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
-
Poor:
Depth < 57 or > 84, Table < 51 or > 85
Emerald & Radiant
-
Ideal:
Depth 63.1-69.9, Table 62-69, Polish & Symmetry Very Good or Excellent
-
Very Good:
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
-
Poor:
Depth < 56.1 or > 84.0, Table < 53 or > 85
Asscher
-
Ideal:
Depth 63.1-69.9, Table 55-64, Polish & Symmetry Very Good or Excellent
-
Very Good:
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
-
Poor:
Depth < 56.1 or > 84.0, Table < 53 or > 85
Marquise, Oval & Pear
-
Ideal:
Depth 59.0-63.0, Table 57-60, Polish & Symmetry Very Good or Excellent
-
Very Good:
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
-
Poor:
Depth < 46.1 or > 71.0, Table < 51 or > 69
Heart, Trillion, Cushion & 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
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.
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.
Flourescence:
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 the GIA website where they discuss fluorescence.
- N = None
- F = Faint
- M or MB or MED = Medium
- S or STR or SB = Strong
- VS or VSB = Very Strong