| Diamond Clarity |
Article Index for Diamond |
Shopping Clarity |
Website Links For Diamond |
Information AboutDiamond Clarity |
| CATEGORIES ABOUT DIAMOND CLARITY | |
| diamond | |
|
Most inclusions present in gem-quality diamonds do not affect the diamonds' performance or structural integrity. However, large clouds can affect a diamond's ability to transmit and scatter light. Large cracks close to or breaking the surface may reduce a diamond's resistance to fracture. Diamonds with higher clarity grades are more valued, with the exceedingly rare "flawless" graded diamond fetching the highest price. Minor inclusions or blemishes are useful, as they can be used as unique identifying marks analogous to Fingerprint s. In addition, as Synthetic Diamond technology improves and distinguishing between natural and synthetic diamonds becomes more difficult, inclusions or blemishes can be used as proof of natural origin. INCLUSIONS AND BLEMISHES There are several types of inclusions and blemishes, which affect a diamond's clarity to varying degrees. Features resulting from Diamond Enhancement procedures, such as ''laser lines'', are also considered inclusions and/or blemishes. Inclusions
Blemishes
CLARITY GRADING Gemological Institute of America (GIA) History In 1952 , Richard T Liddicoat , along with Lester Bensen , Joe Phillips , Robert Crowningshield and Bert Krashes began to work on a new diamond grading system which they called the ''diamond grading and evaluation appraisal''. In 1953 , they released their new system which assessed three aspects of diamonds; ''make'', ''color'' and ''clarity''. They took terminology used in the industry at the time and refined the definitions to produce a clarity scale by which diamonds could consistently be graded. The system at that time contained nine grades, ''flawless'', ''VVS1'', ''VVS2'', ''VS1'', ''VS2'', ''SI1'', ''SI2'', ''I1'', and ''I2''. The ''I'' of the ''I1'', and ''I2'' grades stood for ''imperfect''. During the 1970's two changes were made to the system. Firstly, the ''internally flawless'' grade was added, as GIA noticed that many diamonds were being aggressively cut to remove any surface blemishes, and thereby reducing the cutting quality (''make'') of the diamonds. The ''internally flawless'' grade gave diamond manufacturers a choice to leave blemishes on the surface of the stone, and achieve a grade higher than VVS1. The second change made to the grading system, was the introduction of the I3 grade. This change was made in response to a growing number of diamonds of very low clarity being cut. The last change to the clarity grading system took place in the 1990's when the term ''imperfect'' was updated to ''included''. The GIA grading system today The GIA diamond grading scale is divided into six categories and eleven grades."Diamonds and Diamond Grading" course material - Book 11, Grading Clarity, Gemological Institute of America, 2002 The clarity categories and grades are:
=GIA clarity grading procedure GIA clarity grading is performed under 10x magnification with darkfield illumination. The GIA Gem Trade Laboratory, uses as standard equipment a binocular stereo microscope, that is able to zoom to higher magnifications. These microscopes are equipped with darkfield illumination, as well as an ultraviolet light filtered overhead light. When grading is performed using a 10x handheld loupe, 'darkfield' illumination is more difficult to achieve. The grader must use a lightsource in such a way that the base of the stone is lit from the side, and the crown of the stone is shielded from the light. After thoroughly cleaning the diamond, the diamond is picked up using tweezers in a ''girdle-to-girdle'' hold. The grader views the diamond for the first time through the table, studying the culet area of the stone for inclusions. The diamond is then set down, and picked up with the tweezers in a ''table-to-culet'' hold. In this position the diamond can be studied from the pavilion side, and the crown side, examining the diamond through each facet for inclusions. Once a sector of the diamond has been thoroughly examined the grader rotates the diamond in the tweezer, so that the neighboring sector can be examined. The grader uses darkfield lighting to reveal characteristics, and alternates to reflected, overhead lighting to ascertain whether a characteristic lies within the stone, on the stones surface, or both. If the grader is using a stereo microscope, they may zoom in to a higher magnification to make closer observations of an inclusion, but then return to 10x magnification to make an assessment of it's impact on the clarity grade. If a stereo binocular microscope has been used, a final assessment using a 10x loupe is performed before the final judgement is made on the clarity of the stone. The grader firstly decides the clarity category of the diamond using the keywords; ''none'' (FL, or IF if blemished), ''minute'' (VVS), ''minor'' (VS), ''noticeable'' (SI), ''obvious'' (I). The decision is then made on the grade of the diamond.''Diamond Grading: Lab Manual'' Gemological Institute of America, Carlsbad, 2004 Grading systems by other organizations The clarity grading system developed by the GIA has been used throughout the industry as well as by other diamond grading agencies including the American Gemological Society (AGS), European Gemological Laboratory (EGL), and the International Gemological Laboratory (IGL). These grading agencies base their clarity grades on the characteristics of inclusions visible to a trained professional when a diamond is viewed from above under 10x Magnification . Confédération International de la Bijouterie, Joaillerie, Orfèvrerie des Diamantes, Perles et Pierres (CIBJO) The CIBJO or the ''International Confederation of Jewellery, Silverware, Diamonds and Stones'' developed the ''International Clarity Scale'' for grading diamonds. This clarity scale mirrors the GIA grading scale, except nomenclature varies. The CIBJO system names these clarity grades; Loupe Clean, Very, very small inclusions (VVS1 and VVS2), Very small inclusions (VS1 and VS2), Small inclusions (SI1 and SI2), Pique (P1, P2, and P3). Clarity grading by CIBJO standards is by examination using a 10x Achromatic , Aplanatic loupe in normal light. American Gem Society The American Gem Society grades clarity on a number scale between 0 and 10. These numbers grades correlate almost exactly with the GIA system, but with some differences. The flawless and internally flawless (0) grades are grouped together with notation defining whether the stone is free from external blemishes, the VVS through SI grades are numbered 1 through 6, and then there are four grades 7 through 10 for the included category. Clarity grading by AGS standards requires examination using a binocular stereo microscope equipped with adjustable zoom magnification and darkfield illumination. ''The AGS Way: Diamond Grading Standards'' American Gem Society, 1999 International Diamond Council (IDC) The IDC or the ''International Diamond Council'' uses a very similar standard to CIBJO. IDC ''loupe clean'' stones that have external blemishes have notations made on the grading report. IDC clarity grading is by examination using a 10x Achromatic , Aplanatic loupe in normal light. European Gemological Laboratory The European Gemological Laboratory (EGL) introduced the SI3 as a clarity grade. While intended as a range to include borderline SI2 / I1 stones, it is now commonly used to mean I1's which are "eye clean", that is, which have inclusions which are not obviously visible to the naked eye. CLARITY GRADING CONSIDERATIONS All grades reflect the appearance to an experienced grader when viewed from above at 10x magnification, though higher magnifications and viewing from other angles are used during the grading process. The grader studies the diamond for ''internal characteristics'', and judges them on the basis of five ''clarity factors''; ''size'', ''number'', ''position'', ''nature'', and ''color'' or ''relief''. The clarity grade is assessed on the basis of the most noticeable inclusions, otherwise called: ''grade setting inclusions''. This means that less significant inclusions are ignored for the purposes of setting the grade. However, they may still be plotted onto a diamond plot chart. Accurate clarity grading as with other grading steps must be done with the diamond ''loose''; meaning not set into any mounting. Inclusions are often difficult to see from the ''crown'' side of the diamond, and may be concealed by the setting. Size The first clarity factor which is assessed is a clarity characteristic's ''size''. Larger characteristics are typically more noticeable under magnification, thereby placing the diamond into a lower clarity grade. Number The second clarity factor which is assessed is the ''number'' of clarity characteristics. Generally the more characteristics the lower the clarity grade. This assesment is made by judging how readily they can be seen, not by the actual number of characteristics. Position The third clarity factor which is assessed is the characteristic's ''position''. When an inclusion is directly under the ''table'' of the diamond it is most visible. An inclusion under the table and positioned close to a pavilion facet, will reflect multiple times around the stone, giving this type of inclusion the name ''reflector''. ''Reflectors'' are graded as if each reflection were an inclusion (although in plotting the diamond it is only plotted once). For this reason ''reflectors'' have a greater impact on the clarity grade. Inclusions become less visible when they are positioned under the ''crown'' facets, or near the ''girdle'' of the stone. These inclusions may often be more easily seen from the ''pavilion'' side of the diamond than from ''crown'' side of the diamond. In addition the position of large ''feathers'', ''knots'' and ''included crystals'' positioned where they extend to the girdle or crown of the stone, effect the clarity grade. Diamonds worn in jewelry typically will withstand breakage, however inclusions of this ''nature'', in these positions, can pose a risk for further extension of the break in the structure of the diamond. Inclusions that are judged to pose at least a moderate risk of breakage to the stone are graded in the ''included'' category. Nature The fourth clarity factor which is assessed is a characteristic's ''nature''. The characteristic's nature determines whether it is ''internal'' where they extend into the stone, or ''external;'' where they are limited to the surface of the stone. Internal characteristics automatically exclude the diamond from the ''flawless'', and ''internally flawless'' categories. External characteristics exclude the diamond from the ''flawless'' category. A diamond's internal characteristics can be a; ''bruise'', ''cavity'', ''chip'', ''cleavage'', ''cloud'', ''crystal'', ''feather'', ''grain center'', ''indented natural'', ''internal graining'', ''knot'', ''laser drill hole'', ''needle'', ''pinpoint'', or ''twinning wisp''. A diamond's external characteristics can be an; ''abrasion'', ''natural'', ''nick'', ''pit'', ''polish lines'', ''polish mark'', ''scratch'', ''surface graining'', or ''extra facet''. The ''nature'' will also detail whether an inclusion poses a risk to the stone. Inclusions that cause or may cause a break in the crystal structure (included crystal, feather, knot, cleavage) are considered alongside their ''position'', to assess whether they pose a moderate level of risk for further breakage. Color or Relief The fifth clarity factor which is assessed is the ''color'' and ''relief'' of clarity characteristics. Characteristics that contrast with the surrounding diamond are said to have ''relief''. The degree to which this color and relief is noticeable affects the clarity grade of the diamond. Colored inclusions invariably show contrast and are more easily seen. An exception is a black ''pinpoint'' inclusion which is often more difficult to see than a white ''pinpoint''. RARITY AND VALUE Diamonds become increasingly rare when considering higher clarity gradings . Only about 20 percent of all diamonds mined have a clarity rating high enough for the diamond to be considered appropriate for use as a gemstone; the other 80 percent are relegated to industrial use. Of that top 20 percent, a significant portion contains an inclusion or inclusions that are visible to the naked eye upon close inspection. Those that do not have a visible inclusion are known as "eye-clean" and are preferred by most buyers , although visible inclusions can sometimes be hidden under the setting in a piece of jewelry. The most popular gem diamonds fall within the VS and SI grades with FL, IF, and even VVS stones commanding significant premiums , while I stones are shunned by most buyers . FL and IF stones are sometimes referred to as "museum quality" or "investment grade" to denote their rarity , although the term "investment grade" is misleading as diamonds have historically been Illiquid and questionable stores of value. CLARITY ENHANCEMENT See Also: Diamond enhancement Laser "drilling" involves using a laser to burn a hole to a colored inclusion, followed by acid washing to remove the coloring agent. The clarity grade is the grade after the treatment. The treatment is considered permanent and both the GIA and AGS will issue grades for laser drilled diamonds. Reputable vendors should disclose that laser drilling has been used. Clarity can also be "enhanced" by filling the fracture much like a car windshield crack can be treated. Such diamonds are sometimes called " Fracture Filled Diamonds ". Reputable vendors must disclose this filling and reputable filling companies use filling agents which show a flash of color, commonly orange or pink, when viewed closely. There is a significant price discount for fracture-filled diamonds. The GIA will not grade fracture-filled diamonds, in part because the treatment isn't as permanent as the diamond itself. Reputable companies often provide for repeat treatments if heat causes damage to the filling. The heat required to cause damage is that of a Blowtorch used to work on settings, and it is essential to inform anyone working on a setting if the diamond is fracture-filled, so they can apply cooling agents to the diamond and use greater care while working on it. SEE ALSO REFERENCES |
|
|