DIAMOND GRADING
The first thing you must learn is the 4"Cs of diamonds, that's Cut, Color, Clarity and Carat weight. These four items are what makes the worth of the diamond you are buying.
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CUT
Picture of different shapes
Many people confuse cut with the shape of a diamond.
Diamonds are cut in many fancy shapes; the most popular are round,marquise,
oval, pear , heart or emerald-cut. Among them, however, the classic is the round brilliant. This style of cut has experienced the longest development.
Uncut diamonds give no hint of the unique optical properties of the cut stones.Rough diamond hides it beauty beneath a yellow,brown or grey tinted "coat", a non-transparent skin which covers many rough stones.Only cutting
can transform the unattractive "pebble" into that crystal-clear stone which, in clarity, lustre and magical scattering of prismatic colors, surpasses all other precious stones and has fascinated men for centuries.
The beauty of a cut diamond resides not only in an innately favorable body color, by which the human eye is generally first attracted.It lies, rather, in its superlative optical properties, particularly its high refractive index and color dispersion.
Maximum brilliance is not only the result of the practical experience and masterly craftsmanship of the cutter; what is needed rather, is the knowledge and application of physico-optical laws in developing an optimal form of cut.
COLOR
color-grading
The color of gemstones is one of their most characteristic features; and,
equally, constitutes one of the most important,for it is color which strikes human eyes most strongly. It is produced in gemstones by the absorption of light.
The individual color components of which white light is composed are variously absorbed in gemstones according to the atomic structures proper
to the gemstone varieties and their chemical composition.
The color palette of diamond is very richly varied; it ranges from pink through red, blue, green, yellow and brown even black diamonds. The rarest color occurring in natural diamonds is red, followed by green, blue, purple and brown.
Colored diamonds in the trade go under the name of fancy colors. because of their rarity they are held in very high esteem, especially when the color displays an intense saturation.
The most valuable diamonds, however, are the completely colorless stones- in this respect diamond is the only gemstone whose colorlessness renders it more valuable.
Contrasting with the intensely colored diamonds are the far more common naturally occurring diamonds with a slight to obvious yellow saturation.
In commercial color grading these yellow tinted diamonds are grouped in the first place with the colorless stones.
CLARITY
The process of the growth of a diamond in the interior of the earth did not occur evenly, but in several phases. In these various phases, the conditions- pressure, temperature and cooling- did not always remain constant. Inhomogeneities occurred, which are now found as internal features, the so-called inclusions. They are present in the shape of clouds ,they form fracture-, cleavage-or tension crack, or they constitute enclosed minerals which were present during the growth process of the diamond. All such inclusions often serve today as diagnostic, identification features and are an indication of the natural origin of the stone.
CLASSIFICATION
Internally flawless( or Loupe clean) :A diamond can only be designated as flawless if it is shown to be completely transparent and free from inclusions under ten times magnification.
VVS : Very, very small inclusions, very difficult to recognize under ten times magnification.
VS : Very small inclusions, difficult to recognize under ten times magnification.
SI : Small inclusions, easily discernable under ten times magnification , not visible through the crown with the naked eye .
I :From Inclusions can be seen easily under ten times magnification till large and/or numerous inclusions, easily visible with the naked eye.
CARAT-WEIGHT
Weight table
Besides cut,color and clarity, weight provides a further basis in the valuation of a diamond.
The weight of all gemstones is measured and counted in carats, commercially abbreviated to "ct".
It is only since the beginning of this century that the carat weight has been adapted to the metric system and is now used internationally. It is today standardized just as the ten times magnification, and the use of master stones for color determination of diamonds.
The unit of weight is established as follows:
one metric carat =200 mg =1/5 gram.
The carat is subdivided into tenth, hundredth and lately even thousandth. Very small brilliants are measured in "points"; one "point" is equal to one hundredth of a carat (0.01).
A carat is also subdivided into "grains" - a unit of weights used for pearls- where
one carat = four grains
a one-carater therefore is also a four-grainer.
