Conventional diamonds are graded by how closely they achieve absolute colorlessness. Most stones usually have a slight trace of yellow, brown or gray. In the late 1950s the Gemological Institute of America (G.I.A) developed a system using an alphabetical letter to indicate the depth of color in a diamond. G.I.A assigned D the best color. Colors range from D (colorless) to Z (light yellow).
To color grade a diamond the jewel is compared to diamonds of known color, called master stones. The highest master stone is an E, any diamond lighter than the E master is a D. Each letter grade encompasses a range of colors rather than one specific hue. There is no one exact color. For example, an H diamond can be a good H, very close to the H master, or it can be a bad H, closer to the I master. As long as a diamond is between the H and I master stones, it is considered an H color diamond.
The difference between each master is minute. Mounted diamonds cannot be graded as consistently as loose diamonds due to the light reflected from their mountings. Without master diamonds and a proper grading environment a loose diamond can only be approximated to within two grades. A mounted diamond can only be approximated to within three or four grades.
Even experienced diamond graders have a difficult time distinguishing between color grades without the proper environment for analysis. When purchasing a diamond don’t take chances, always make sure the stone is accompanied by a certificate from a leading laboratory such as E.G.L or G.I.A.
Clarity determines the amount and type of imperfections, or inclusions, in a diamond. These marks serve as fingerprints, helping to identify a particular diamond, and to distinguish it from a simulated stone. Imperfections may interfere with the play of light in a stone, or in extreme cases, its structural integrity. Inclusions are determined through examination with a 10x magnification lens.
While determining the diamond’s clarity grade the following are considered:
Size – How small or large are the inclusions?
Number – How many inclusions are there in the diamond?
Position – Where in the gemstone are the inclusions?
Nature – What kind of characteristics are there? Do they harm the stability of the stone?
Color or Relief – How large and how visible are the clarity characteristics?
Clarity Grades – Clarity grades range from flawless for a perfectly clean diamond even under microscope, to an I3 stone so full of inclusions and blemish, it can be unattractive and fragile. The cleaner the diamond the rarer and more expensive it will be.
|Flawless||No internal or external flaws|
|IF – Internally Flawless||No internal flaws, slight external blemishes|
|VVS1, VVS2 – Very Very Slightly Included||Very difficult for a professional to see inclusions under 10X magnification|
|VS1, VS2 – Very Slightly Included||Minor inclusions ranging from difficult to somewhat easy to see|
|SI1, SI2 – Slightly Included||Easy (SI1) or very easy (SI2) for a professional to see inclusions under 10X magnification, might be visible to the naked eye.|
|I1, I2, I3 – Included||Inclusions are visible to the naked eye face up.|
Diamond cut is the human contribution to a diamond’s beauty, brilliance and fire. The execution of this C can affect a stone’s clarity, color and carat weight. A well-cut loose diamond will allow light to enter the stone, reflect off of the internal facets and through the top, creating the brilliance and fire only a diamond can achieve. Diamonds can be cut to virtually any shape and size. Some popular forms include oval diamonds, marquise, pear, heart, emerald, princess, radiant and the most popular, the round brilliant.
A diamond is divided into three sections:
The Crown –The upper section of the diamond
The Girdle – The rim separating the crown (top) from the pavilion (bottom)
The Pavilion – The lower section of the diamond
A round brilliant diamond has between 57 and 58 facets (depending on whether the bottom most facet was polished) divided into 7 different parts. On the crown/. is a large octagonal table surrounded by 8 triangular star facets; 8 kite bezel planes and 16 triangular upper girdle surfaces, arranged in pairs that circle the crown’s perimeter. A culet on the pavilion connects 8 elongated, kite-shaped pavilion mains to the girdles’ edge. Separating the pavilion mains are 16 elongated, triangular lower girdle facets arranged in pairs.
Facets are divided as follows:
A Table – 1
B Bezel – 8
C Star – 8
D Upper girdle – 16
E Pavilion Main – 8
F Lower Girdle – 16
G Culet – 1
Diamond Proportions – Today’s designs are the result of hundreds of years of experience. In 1919 a Russian mathematician by the name of Marcel Tolkowsky calculated the proportions of the facets in a round diamond that would bring an ideal balance between brilliance and dispersion.
When cutting a diamond, cutters have to choose between optimizing weight and potential profits, or optimizing beauty. Many cutters sacrifice splendor instead of size. These choices are condoned because of stores that have been keeping customers in the dark and pushing carat rather than beautiful proportions. Most consumers have yet to understand that two diamonds with the exact same weight, color and clarity can be purchased up to 40% cheaper if the cut is subpar. This trade secret allows some jewelers to buy very poor makes and sell them in turn at prices reserved only for wonderfully cut stones.
Every diamond lab has small variations of what a beautifully cut diamond’s proportions should be. Leading gemology labs agree on the following proportions:
|Table %||53-61%||The percentage of the table relative to girdle diameter|
|Crown angle||33-36 degrees||The angle between the bezel facets and the girdle|
|Girdle thickness||Thin – Slightly thick||Assessing girdle thickness is done by eye; it ranges from extremely thin to extremely thick.|
|Depth %||59-64%||The height of the diamond expressed as a percentage of girdle diameter|
|Culet size||None – Very small||Assessing culet size is done by eye; it ranges from pointed to extremely large.|
|Symmetry||Good – Excellent||The equality between corresponding parts of the diamond graded from poor to excellent|
|Polish||Good – Excellent||The quality of the facets’ polish graded from poor to excellent|
Cut Proportions – Deviations from even one of these parameters can noticeably change the appearance of the diamond.
Let’s use as an example a diamond with the following parameters: 58% table, 34.5 degree crown angle, slightly thick girdle, 64.5% pavilion depth %, no culet, excellent symmetry, very good polish.
To the inexperienced eye this is a beautiful diamond. Other than the diamond’s depth all the proportions are ideal. A closer look reveals that the stone is too deep causing light to leak out, resulting in poor brilliance.
The most precise of the 4Cs,“carats” determine the size and weight of a diamond. It is not to be confused by the similar sounding “karat,” which determines the purity of gold. The term for metric carats is derived from well before the advent of digital scales, when uniformly weighed carob seeds were used to measure a diamond’s size.
One carat (ct) equals 1/5 of a gram. Every carat is divided into 100 points (pt). Therefore, a 50-point diamond is also called a ½ carat. Diamond weight is so precise that polished diamonds are weighed to a thousandth of a carat and then rounded off to the nearest hundredth (point,) for example a stone could measure .37pt. Diamonds weighing less than 20 points are often called melee. Another term often used is grain or grainer.
A grain equals one-quarter (0.25) of a carat. A 75-point diamond would be called in the trade a three grainer and a one-carat stone may be called a four grainer. Loose stones may be weighed directly on a scale but mounted stones can only be estimated by plugging their measurements into a mathematical equation. Another quick way of estimating mounted round diamonds is by measuring the diameter of the diamond and comparing it to a size chart.
Magic Sizes – Since the price of diamonds is based upon rarity, the larger the stone, the rarer the diamond and the higher the price per carat. A one-carat stone is much less common than two half-carat stones, and is considerably more expensive.
Magic size plays a significant role in pricing diamonds. People tend to prefer a one-carat stone over a nearly one carat diamond. For this reason alone a 1.00ct diamond is worth much more than a 99-point diamond. Even the most experienced diamond dealer cannot tell the difference without a specialized scale. Could you visualize less than one fourteen-thousandth of an ounce? Yet there are people willing to pay hundreds, sometimes thousands, of dollars for this minute difference in engagement & anniversary diamond rings.
A large diamond is not necessarily a beautiful diamond. There are a number of factors to consider before purchasing a jewel.
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