FACTORS THAT DETERMINE DIAMOND VALUES
The traditional ‘4 C’s’ determine the value of the diamond. The ‘4 C’s’ are clarity, colour, cut and carat weight. Cut will be subdivided into the ‘finish’ and ‘proportions’. As far as carat weight is concerned diamonds logarithimcally increase in value. This means that a half-carat diamond will have a higher value than two one-quarter carat diamonds. Likewise, a 1 ct. diamond will have a significantly higher value than two one-half carat diamonds. The reason for this is due to the fact that the larger the diamond is the harder and more rarer it is to find the original crystal from which the diamond is cut.
How to properly view a diamond internally
When contemplating purchasing a diamond you should ask the jeweller for a 10X corrected eye loupe in order to properly examine the diamond. A stereoscopic binocular microscope with dark field illumination set at 10X is better still but not essential. Dark field illumination simply means that the diamond is held against a black background in the microscope and light enters the diamond from the sides and therefore all internal inclusions are easily visible. The circular well within the microscope is lit and the diamond is held at the top of the well. In this manner a great majority of the light enters the sides of the diamond and the clearest internal view of the diamond is obtained. Bring the eye loupe right up to your eye in one hand and hold the diamond ring or the loose diamond in a tweezer in the other hand. At this stage bring the diamond to a distance of approx. one inch away from the eye loupe and focus until the entire interior of the diamond is in clear view. Try to locate any surface blemishes or internal inclusions within the diamond. You may have difficulty at the beginning so ask your jeweller to help you spot any inclusions present. Be sure that the loupe is 10X since clarity standards and grades are determined under 10X power.
If you view the diamond from the side you will most likely notice a somewhat thick whitish line midway from the girdle to the point of the diamond. A lot of clients come to the IGS Inc. lab inquiring specifically about this whitish line that they see. The clients are very nervous about this line and think that it is a crack in the diamond which they did not notice when they were purchasing the diamond. This line is simply the replection of the girdle in the pavilion facets. The pavilion acts as an internal mirror and is simply reflecting the girdle. This is a normal type of reflection and this reflection should be there.
Do not touch a loose diamond with your hands as this will leave a film and grease layer over the diamond. To pick up a loose diamond with a tweezer, place the diamond table down on a flat surface and position the diamond between the two arms at the end of the tweezers and grasp the diamond with the tweezers from the girdle edge at each side.
Be sure that you have access to good lighting. The best lighting for viewing diamonds is a combination of white fluorescent light and incandescent light. Strong halogen quartz lights tend to give diamonds a slightly yellowish tinge.
After you have the diamond focused under the loupe look at the diamond from an angle instead of straight down in order that plenty of light is available. Look through the table or large flat surface on the top of the diamond in order to view the interior of the diamond. Observe the diamond from the sides in order to view the girdle. All inclusions should be visible from the table. Turning the diamond upside down and looking at the bottom or pavilion of the diamond usually results in viewing reflections off the pavilion surface.
Diamonds are carefully assigned a clarity grade by a trained observer or gemmologist under a 10X magnification. Clarity refers to the relative degree to which a diamond is free from inclusions and blemishes. The clarity grade assigned has an effect on the diamond’s value in the present market. Perfect or flawless diamonds are extremely rare. The effect of very minor inclusions and blemishes on beauty is infinitesimal. On the other hand, a heavily included diamond will not allow the light the freedom of traversing the diamond without being blocked, distorted or deflected and this will ultimately effect the overall brilliancy of the diamond. A diamond of lower clarity may give more satisfaction to a customer for his dollar than a smaller high clarity grade diamond.
The Different Clarity Grades of Diamonds
Let’s discuss exactly what each clarity grade means. Diamonds in the flawless category are free from internal and external blemishes when examined by a skilled observer under 10X magnification.
Diamonds in the internally flawless category have no internal imperfections but some surface blemishes may be present.
The terms VVS-1, very very small 1, and VVS-2, very very small 2, describe diamonds that when viewed under 10X magnification by an expert show only very, very small inclusions which are difficult to be seen. The inclusions should be light colored. The features of the VVS grade are exceptionally difficult to discern. The typical inclusions of this grade are dot-like inclusions. Whether a diamond is VVS-1 or VVS-2 depends on the relative degree to which the minute inclusions are present. If they are present to a minimal degree then the VVS-1 grade is chosen. Just a little added touch to the degree of inclusions will result in a VVS-2 grade.
Diamonds are classified into the VS, very small inclusions grade, when the expert using a ten times magnification can discern very small inclusions which are difficult to be seen. The experienced grader does not find the internal faults at once, but does not have too great difficulties to see the inclusions when he moves the diamond a little from side to side. Typical inclusions of this group are small, light clouds or small light cracks on the girdle as well as single crystals just slightly larger than a dot. Inclusions in this clarity grade should be mainly light-colored. Very small dark inclusions are allowable under the girdle. Depending on the degree of inclusions the diamond is either rated VS-1 having fewer inclusions or VS-2 having just a little higher degree of inclusions.
The SI or ‘small inclusions’ term comprises diamonds which, when viewed with ten times magnification have small inclusions. These are usually easily seen by an experienced grader. As soon as he observes the diamond with the right magnification the inclusions jump into the field of view and should be light and around the girdle there can be small, dark inclusions. Again, depending on the degree to which inclusions are present the diamond is either rated SI-1 or SI-2, with the SI-1 having a lesser degree of inclusions than an SI-2.
The I-1 (Imperfect-1) grade sometimes is referred to as the P-1 or (Pique’-1) grade. The word pique’ is a French word meaning ‘mark’ or ‘spot’. The I-1 grade comprises those diamonds which when viewed with ten times magnification show several inclusions at once but which do not diminish the brilliance. With the naked eye, when viewed through the crown, these faults, even in larger diamonds, are only discernible with difficulty. Typical defects of this group are larger colored inclusions as well as larger cracks or plane-like inclusions.
The I-2 (Imperfect-2) or P-2 grade is comprised of diamonds with larger and/or numerous inclusions which can be seen with the naked eye through the crown and which may diminish the brilliance somewhat even in smaller diamonds. There might be dark inclusions or numerous light-colored features. Another characteristic is larger cracks which may influence the durability of the stone and they could possibly expand under stress into the interior of the diamond, especially if they are to be found near the girdle. I do not recommend purchasing a diamond with a clarity grade of I-2 or lower since the multitude of inclusions will tend to block or impede the passage of light through the diamond and thus reduce the overall brilliancy. Also, the presence of larger inclusions especially cleavage-like inclusions will create a certain amount of internal strain that will ultimately weaken the diamond.
However, there are to be found large diamonds with an I-2 clarity that seem to be quite brilliant and are quite strong. Ask your independent gemmologist his opinion on any I-2 or lower clarity diamond. Ask him specifically about reduced brilliancy and the overall strength of the diamond.
The I-3 (Imperfect-3) or P-3(Pique’-3) clarity grade is the lowest grade of clarity and is comprised of large and/or numerous inclusions which are easily visible through the crown with the naked eye. The number and size of inclusions diminish the brilliance considerably.
BE VERY CAREFUL WHEN PURCHASING MARQUIS AND PEAR-SHAPED DIAMONDS IN REGARDS TO INCLUSIONS THAT MAY BE PRESENT TOWARDS THE TIPS OF THESE DIAMONDS. INCLUSIONS ARE VERY HARD TO NOTICE IN THESE PARTICULAR AREAS AND SEEM TO GO UNDETECTED. TOWARDS THE TIPS OR POINTS OF THE DIAMONDS THERE ARE A GREAT MANY REFLECTIONS THAT MAKE INCLUSION DETECTION HARD. ASK YOUR JEWELLER TO PARTICULARLY NOTE THESE AREAS OF FANCY CUT DIAMONDS.
The Colour Grading of Diamonds
In order to colour grade a diamond, the loose diamond or diamond ring is viewed in a special apparatus referred to as a Diamond Lite. (See Section Three, paragraph 3)
Just as a matter of interest it is the presence of nitrogen that causes the yellowish tinge to appear. One part in a million will cause the yellow tint to appear in a K colour diamond.
Although diamonds range from colorless to almost every hue, the vast majority contains some tint of slightly greenish-yellow. Thus, diamond colour grading is usually a comparison of diamonds having faint tints of this slightly greenish-yellow hue. The starting point for colour grading is the diamond without the slightest tint of colour. The next one or two grades of any detailed colour grading system are based more on a difference in transparency than on tints of colour. Subsequent grades increase in colour to the point where the light yellow classification is reached.
With respect to the colour lettering grades D and E refer to the rarest white diamonds. F, G & H refer to white diamonds. Mounted diamonds that are either D E F G or H will appear colorless except to the trained eye. I, J, & K diamonds are referred to as tinted white. I, J, & K diamonds that are mounted will appear colorless but larger diamonds will appear to be tinted white. Any diamonds from L to R will appear yellowish. Mounted diamonds from L to R will display a yellowish tint even to the untrained eye. Diamonds from R to X will appear yellow either as loose diamonds or mounted diamonds.
Diamonds have been found and cut in some tones and intensities of each of the six spectral hues. However, they are usually either colorless or range from very light to strongly colored yellow or brown. The yellow is usually slightly greenish, a characteristic that becomes obvious only when a number of yellow diamonds are grouped together. Both the relative rarity of the colorless diamonds and the fact that they are considered more attractive by the majority of jewellers and customers has made them the most valuable of the usual range of diamond colours.
Despite the common usage of terms such as “blue-white” and ” gem blue”, blue diamonds are exceedingly rare. Most diamonds that are referred to by one of these terms in the trade are actually very faintly tinted with yellow, although some are colorless. Of the thousands of diamonds submitted to the Gemological Institute of America for colour grading, not more than one in 500 has shown even the faintest trace of blue body colour in incandescent light. Fluorescent diamonds that are exposed to sunlight may display a slight bluish overcast.
The term “blue-white” in diamonds actually refers to a particular type of white diamond from the Jagersfontein Mine in South Africa that is very slightly bluish, usually owing to its strong blue fluorescence. The term “blue-white” arose from such stones. ‘Jagers’ are very few indeed and it is incorrect to call other stones “blue-white”.
As yellow and brown in diamonds increases from the colorless end of the usual grading scale, value drops to the point at which the colour becomes deep enough to be an asset. In other words, faint tints of yellow or brown, in the opinion of many jewellers, detract from a diamond’s beauty, whereas attractive deep tones of these colours increases desirability.
The possible cutting grades in descending order are as follows:
1. Very good.
2. Very good-good.
The assigned grade is determined by comparison with the ideal American standard cut diamond. The cutting grade assigned to a diamond is determined by the following factors: the proper crown and pavilion angles, table and depth percentage, polish, girdle thickness and finish, culet size, facet alignment and symmetry as well as minor symmetry faults.
The term ‘very good cut’ is used for diamonds within the tolerances of the standard American ideal cut.
The term ‘good cut’ is used for diamonds just outside the tolerances of the standard American ideal cut.
The term ‘ medium cut’ is used for diamonds of average proportions.
The term ‘poor cut’ is used for diamonds with distinctly reduced light effect to the untrained eye.
Generally, a good to very god cut has a table size from 53 to 60%, crown angles that are 34 to 35 degrees and a medium to slightly thick girdle. The polish and symmetry is very good to excellent. In diamonds half a carat or less larger tables up to 62% are acceptable.
Generally, a medium cut diamond has a 61 to approx. 65% table, a 32 to 34 degree crown angle and a thin to thick girdle. The diamond would have a pavilion depth of approx. 42 to 44% The polish and symmetry are good.
Generally, a fair cut will range in between the description as seen above in the medium cut and the description as seen below in the poor cut.
Generally, a poorly cut diamond will have a 65 to 70% table, approx. 30 to 32 degrees crown angle, and a thin or very thick girdle. The pavilion depth may range from approx. 41 to 46%. The polish and symmetry may be fair.
The poorest cut diamonds will have table sizes larger than 70%, crown angles shallower than 30 degrees, and knife-edged or very thick to extremely thick girdles. The pavilion depth may be shallower than 40% or deeper than 46%. The polish and symmetry may be fair to poor.
CUT PROPORTIONS MAY OVERLAP INTO MORE THAN ONE GRADE. POLISH AND SYMMETRY ARE COLLECTIVELY KNOWN AS FINISH.