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If the stone is cut too shallow, much of the light may leak out the bottom of the stone. The pictures of the deep stone and the shallow stone have been shown exaggerated for illustrative purposes oThese may include the quality of the polishing,tiffany silver ring, the symmetry of the diamond, variances in the quality of the diamond material (which resulted from changing conditions of temperature and pressure in nature as the rough diamond crystal was being formed), and numerous other gemological factors.
Carat weight is the last major criterion that jewelers take into consideration when evaluating a diamond. Today,Gucci Rings, digital scales make weighing diamonds both fast and accurate. The weight of a diamond is expressed in carats and points. There are one-hundred points to the carat.
These are the basic characteristics of a diamond that will be discussed in this booklet. In reality, however, there are many additional characteristics that the gemologist takes into consideration when evaluating a diamond. One of the most important of these non-measurable characteristics is the transparency of the diamond material itself. This refers to whether the material is "grainy" in nature or whether it is of the more desired "crystal" quality.
Clarity grading is accomplished by inspecting the diamond under ten-power magnification, using either a microscope or a jeweler's loupe. The clarity grading scale begins with a rating of flawless. A flawless diamond has no inclusions under ten-power magnification when viewed by a trained eye. A diamond that is 48 points, for example, is 48/100 of a carat -- or slightly under one-half carat.
As diamonds increase in size, the price per carat goes up very rapidly. A one carat diamond of a particular quality may be twice the weight of a half-carat diamond of the same quality, but it may cost three times as much. The explanation for this is simple.
As stones increase in size, they become rarer and their price per carat increases.
There is also an SI-3 grade between SI-2 and I-1 that is used by some laboratories. When judging clarity, the jeweler considers the size, nature, number, position, and relief of the inclusions and then makes an educated decision as to where this diamond would fall on the scale.
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发表于 2009-9-23 11:58:01