|There are 4 different factors that make up a diamond, they are Carat, Cut, Clarity, and Color. Carat refers to the weight of the stone; cut describes the basic shape, or shapes of the stone; clarity is a description of the imperfection(s) in the stone; and color refers to how clear to how yellowish a diamond is.
Size is the most obvious variable in diamonds, but it is the least important in comparison with quality and brilliance. One carat is equal to 1/5 of a gram (200 mg) and is divided into 100 “points” (a 50 point diamond is .50 cts.).
If we express the relationship between size and price: as size increases, price per carat increases exponentially.
If we were to advertise 1/2 carat diamonds, that could actually represent a stone .46 ct. to .69 ct. without misrepresentation. However, there are two separate price categories varying by as much as 10% per carat. .46 to .49 ct. is a small category called a “light half.” This “light” category is also represented one other time, a “light carat,” it equals .90 to .99 ct. Remember, one must be careful to keep track of price changes as the size category changes.
The specific size categories are:
||.18 – .22 ct.
||.50 – .69 ct.
||.23 – .29 ct.
||.70 – .89 ct.
||.30 – .37 ct.>
||.90 – .99 ct.
||.38 – .45 ct.
||1.00 – 1.49 ct.
|lt. 1/2 ct.
||.46 – .49 ct.
But no matter how experienced someone is, they cannot look at a stone and identify a difference of a light-half and a half-carat diamond since cut changes so much.
This is the only thing man does to the stone, and it is the only characteristic that produces scintillation or sparkle in it. Cut is also the most important variable that effects the diamond’s performance on a day-to-day basis.
We measure the success of the cut in three areas on all stones. The widest part of the diamond is called the GIRDLE and it separates the diamond top to bottom. From the girdle to the top of the stone is the CROWN, from the girdle to the bottom of the stone is the PAVILLION, and the large surface on top is the TABLE.
Using the individual stone’s GIRDLE diameter as the 100% to which all parts are measured against, the cutter strives for the crown to be 15.4%, the table to be between 53% and 57%, and the pavilion to be 43%. If this is true, what results is total internal reflection. This means that light traveling directly into the stone through the table, is reflected off the pavilion and returns back through the table to your eye. This light creates a flash of white light called brilliance.
When light travels through the crown facets and is broken into the spectral colors, it is called dispersion or fire. The table and crown proportions maximize both brilliance and dispersion.If the pavilion is cut too deep, light leaks out the side and is not returned to your eyes. If the pavilion is too shallow, the light passes straight through the diamond. This is the case when a diamond appears larger than it really is (i.e. a 3/4 ct. stone looks like or has the same diameter as a 1 ct. stone).
On a very real level, cut makes a 5 to 15% variance in the prices of cut diamonds. A Class I, or well cut diamond, will have a crown between 13% and 16%, a table less than or equal to 60% and a pavilion between 42% and 44%. Within these parameters, it will ensure that the diamond is cut well and produces superior scintillation (combination of brilliance and dispersion) that will show even when the diamond has a layer of skin oil, lotion, etc. on the back.
Clarity is a relative evaluation of how much contamination exists in the stone. That contamination consists of diamond crystals encapsulated within (dark, white or colorless), liquid or gas filled bubbles, or irregularities in the crystal structure called feathers. We call these contaminations, inclusions, because they are what the diamond cutters decide to include in the final cut diamond.
We clarity grade stones on a scale that is at best Flawless and at worst Imperfect. The scale is broken into groups: Flawless (FL), Very Very Slightly Imperfect (VVS), Very Slightly Imperfect (VS), Slightly Imperfect (SI) and Imperfect (I). There are also subgroups within: VS1, VS2, SI1, SI2 etc…
From SI1 and above (towards flawless) you need 10x magnification to see any inclusions inside the stone. From I1 and below, inclusions are visible without any magnification (your naked eye). SI2 becomes a bridge between these groups; looking at the stone from the top you need 10x magnification to see inclusion, but if you turn the stone over, inclusions are visible without magnification.
A hand help loupe is a great tool to use for magnification, however, it can be cumbersome to handle and difficult to see inside the stone. A binocular microscope is easier to use and fully discloses all aspects of the diamond.
Diamonds naturally bear a yellow body color. We evaluate color based on how little or how much yellow is visible. The color grading scale begins with the letter D and continues through X. D, E, and F are the top Colorless grades. G and H, and I and J are the next two groups of Near Colorless; K and below, we see yellow in the stone. The letter grades are not absolute values of color, but rather, small ranges themselves.
|Very Light Yellow
Diamond color is best judged under corrected northern daylight, unmounted and through it’s side on a stark white background. Be very careful when viewing stones under showroom lighting (florescent and incandescent). A mounted I color diamond can be made to appear the same as a mounted E color diamond.
Although the Round Brilliant Cut is optically the most perfect, several fancy shapes are also very beautiful if properly cut. Variation of the Brilliant cut include the oval, pear-shape (pointed at one end) and the marquise (pointed at both ends). Other shapes and cuts include the Emerald, Princess, Radiant, and Trillion cut.