If you are planning on purchasing a diamond, it is important that you know as much as possible about how diamonds are classified to enhance the joy of your gift and the value of your investment. Four factors are considered for grading quality, commonly referred to as the 4Cs:
Another "C" one might consider is certification. Our education center explains each of these factors in detail.
Cut and shape are probably the most confusing aspects of a diamond's quality and value. Diamonds of the same Color, Clarity, and Carat weight can have a difference of up to 40% in value depending on the cut and shape of the stone.
The shape of the diamond refers to the overall appearance of the stone, i.e., the geometric shape of the stone. Some of the most popular shapes are:
Round Brilliant Cut
Round outward appearance with kite and triangle shaped facets radiating from center to the girdle (brilliant facet arrangement). Most brilliant, most popular, and most valuable.
Princess Brilliant Cut
Square or rectangular outward appearance; brilliant facet arrangement. Second most popular, lends it self to modern or contemporary designs.
Canoe or football shaped outward appearance with brilliant facet arrangement. Also known as the Navette.
Mostly rectangular outline, can also be square, rows of parallel facets, and diagonally cut corners. Classic and traditional.
Oval Brilliant Cut
Oval or elliptical outline with brilliant facet arrangement.
Pear Brilliant Cut
Pear or tear drop outline with brilliant facet arrangement.
Radiant Brilliant Cut
Rectangular or square outline, with 70 kite and triangle shaped facets.
Heart Brilliant Cut
Heart shaped outline with brilliant facet arrangement.
Trilliant Brilliant Cut
Triangular outline with brilliant facet arrangement. Sold mostly as matched pairs for accent stones.
The cut of a diamond refers to how symmetrical and proportional the facets are arranged on the stone. The skill and accuracy the cutter uses in placing these facets at their correct angles and percentages is crucial for the return of maximum light to the eye.
A Round Brilliant Cut, being a symmetrical sphere, is the best example of how to demonstrate the effect light has on the cut. White light, when entering a diamond, is refracted and then reflected from the bottom (pavilion facets) and returned through the top (crown) of the diamond. Because of a diamond's extraordinary ability to break white light, what the human eye actually sees is an array of vivid spectral colors that is known as "dispersion" or fire. Another attribute of a diamond is hardness. Hardness gives a diamond an unsurpassed adamantine luster, which allows diamonds to reflect more white light (brilliancy) than any other gemstone. What the eye ultimately sees when an ideally cut diamond is viewed in light is a spectacular combination of dispersion (fire), brilliancy (flashes of white light returning from internal facets), and scintillation (flashes of white light returning from the surface).
When a diamond is cut too shallow, much of the light is lost through the bottom and not returned to the eye. This "windowing" effect tends to make the diamond lifeless and somewhat glassy in appearance. On the other hand, on a diamond that is cut too deep, much of the light is reflected out of the opposite side of the bottom of the pavilion. This tends to make the diamond appear dark in the center and provides little light return.
In 1919 a mathematician, whom also had an interest in diamonds, wrote a doctoral thesis outlining the proper proportions for maximum light return within a round brilliant cut diamond. Marcel Tolkowsky devised, mathematically, the cut parameters that would produce the maximum light return with a balance of brilliance and dispersion. Diamonds cut to his calculations are termed as an "ideal cut" or a "Tolkowsky-Ideal cut". Unfortunately, due to the weight loss in a diamond cut to these standards, most diamonds on today's market are not cut exactly to these specifications.
Fancy shapes are any other shape than Round. Being irregular in shape, these stones do not have a model for ideal proportions as do round stones. Fancy shapes are judged on the length to width ratio of the stone and then on the amount of 'bow tie" (optical effect created with the loss of light through the bottom of the stone). Here are some basic guidelines to follow for each particular shape.
The clarity of a diamond is related to its purity. In other words, the freer the diamond is of imperfections, the more rare and more valuable the stone becomes. Diamonds are graded using a universal grading scale for clarity that was designed by Robert M. Shipley of the Gemological Institute of America in the 1940's. The grading scale takes into account the ease of finding inclusions, as well as the number, nature, and location of the inclusions. A summery and explanation of the clarity scale can be found below.
No inclusions or external blemishes can be found by a skilled grader, using 10x magnification.
IF (Internally flawless)
No inclusions, only slight surface blemishes, can be found by a skilled grader, using 10x magnification.
Vvs1 (Very, Very slightly included 1)
Extremely difficult to find minute inclusions by a skilled grader, using 10x magnification.
Vvs2 (Very, Very slightly included 2)
Very difficult to find minute inclusions by a skilled grader, using 10x magnification.
Vs1 (Very Slightly included 1)
Difficult to see minor inclusions by a skilled grader, using 10x magnification.
Vs2 (Very slightly included 2)
Somewhat difficult to see minor inclusions, using 10x magnification.
Si1 (Slightly included 1)
Easy to find noticeable inclusions, using 10x magnification.
Si2 (Slightly included 2)
Very easy to find noticeable inclusion, using 10x magnification.
I1 (Imperfect 1)
Obvious and or multiple inclusions under 10x magnification. Often visible to the unaided eye.
I2 (Imperfect 2)
Obvious and or multiple inclusions, easily visible by the unaided eye.
I3 (Imperfect 3)
Extremely obvious and multiple inclusions, extremely easy to see with the unaided eye; Can affect durability.
The color grade refers to how much body color the diamond possesses, if any. Difference from one color grade to another is very subtle and takes years of experience to properly identify. Diamonds range in color from being totally absent of color to having very obvious color. Most diamonds have a hint of yellow or brown due to a high nitrogen component.
The universally accepted color-grading scale was developed by the Gemological Institute of America. The scale ranges from D through Z. DEF graded diamonds are completely colorless, GHIJ are near colorless, and K through Z graded diamonds have increasing amounts of body-color. Most people prefer diamonds whose color grade falls from colorless to near colorless. The G.I.A. scale can be found below.
Natural fancy colored diamonds are rare but can be found in a wide range of colors from intense fancy yellows (canaries), blues, greens and the rarest pinks, purples, and reds. Some fancy colored diamonds on the market today have been enhanced in a laboratory using irradiation and heat. A color origin report from G.I.A or E.G.L. is highly recommended before you consider purchasing a fancy colored diamond.
Diamonds, like any other gemstones, are traded based on their weight or size. The unit of measurement used to describe a gem's weight is carats. A carat is equal to 0.20 of a gram or in other words five carats equals one-gram. A carat is further subdivided into points, like pennies in a dollar. A carat has 100 points. A three-quarter carat diamond equals 75 points or 0.75 of a carat. The larger the diamond, the rarer and more valuable it is.
A diamond certification is an independent grading report of a diamond. It is your third party opinion of the stone quality. Do not rely on an in-house appraisal that cannot be completely unbiased. A grading report scientifically analyzes the Carat weight, Clarity, Color, Measurements, and Proportions, and gives you a plot of the diamond's features. From a certificate or grading report any gemologist can positively identify your diamond. Two of the most highly regarded independent grading laboratories in the world are the Gemological Institute of America (GIA) and the American Gem Society (AGS). These institutions issue written documentation of the diamond's quality.