The 4 C’s
A common misconception is that carat refers to the size of a stone when in fact a carat is a standard unit of measure that defines the weight of a diamond. One carat is equal to 200 milligrams. The term “points” is used when referring to weight, with a one carat being 100 points and a one-half carat diamond being 50 points.
Since a carat is a unit of measure and not size, two diamonds of the same carat weight may appear to be different sizes depending on how the diamond is cut. Some diamonds will have extra weight on the bottom part or pavilion of the stone, and therefore appear smaller.
When discussing the cut of a diamond it is important not to confuse cut and shape. The shape of a stone refers to the overall outward appearance such as, emerald, pear, or round. Cut is in reference to a diamond’s reflective qualities.
Diamond cut is one of the most important of the four Cs, so it is important to understand how this quality affects the values of a diamond. A good cut gives a diamond its brilliance, meaning the bright light radiating from the stone. The angles and finish of any diamond are what determine how the stone refelects light, which leads to brilliance.
The cut of the stone will determine exactly how light travels from the table of the stone and reflects from each side of the pavilion and back out the table to be viewed by the observer. As such cut will determine how light is refracted and how large the stone appears.
The different grade of cut are:
This cut maximizes brilliance by reflecting light thru a slightly smaller table size this refraction also creates a great deal of dispersion or “ Fire”. All Ideal cut stone will be round.
Premium cut diamonds have cuts that are nearly equal proportionally to an ideal cut stone, though they often can be purchased at slightly lower prices than AGS Ideal Cuts. They are intended to provide great brilliance and fire.
A diamond with a very good cut will reflect most of the light which enters, providing a good deal of brilliance. Generally a stone is cut in this way as to maximize the apparent size of the stone at the cost of some of the radiance.
Good diamonds reflect much of the light that enters them. The proportions of these stones will fall outside of the preferred range as they have been cut to create the largest possible diamond from the original rough crystal while still reflecting a good deal of light. A good stone is an excellent choice for those who want to stay within a budget without sacrificing too much radiance or brilliance.
Fair & Poor
A diamond graded as fair or poor reflect a very small amount of the light which enters them. These stone have been cut for maximum size with little regard for brilliance.
Diamonds are graded for clarity under 10x magnification. Clarity grades range from Internally Flawless, meaning the stone shows no blemishes or inclusions even under 10x magnification, to Imperfect 3, meaning blemishes or inclusions are large enough to be seen with the naked eye.
The different grades of clarity are:
FL: Completely flawless
IF: Internally flawless; only external flaws are present, which can be removed by further polishing the stone
VVS1 – VVS2: Only an expert can detect flaws with a 10X microscope. By definition, if an expert can see a flaw from the top of the diamond, it is a VVS2. Otherwise, if an expert can only detect flaws when viewing the bottom of the stone, then it is a VVS1
VS1 – VS2: You can see flaws with a 10X microscope, but it takes a long time (more than about 10 seconds)
SI1 – SI2: You can see flaws with a 10X microscope
I1 – I3: You can see flaws with the naked eye.
Diamonds are graded for color face down, against a white background. Graders are looking at the actual body tone or hue of the stone and comparing it to a set of master stones graded by the Gemological Institute of America. The diamond is then assigned a letter grade as seen on the accompanying chart. Most diamonds used for jewelry purposes fall into the Near Colorless Category – G to J
The Gemological Institute of America (G.I.A.) grades color alphabetically from D (totally colorless) to Z (yellow). For a diamond to be considered “colorless,” the G.I.A. requires that it be a D, E, or F.