DDG Ass #10 Grading Clarity PDF

DDG Ass #10 - Grading Clarity -The GIA Diamond Grading System put an end to that confusion. Since its introduction in 1953, it has given diamond professionals a way to evaluate a diamond and communicate its quality to others. Five Clarity Factors: - Five factors determine the overall impact that an...

DDG Ass #10 - Grading Clarity -The GIA Diamond Grading System put an end to that confusion. Since its introduction in 1953, it has given diamond professionals a way to evaluate a diamond and communicate its quality to others. Five Clarity Factors: - Five factors determine the overall impact that an individual clarity characteristic has on a stone’s appearance and grade: Size, Number, Location (position), Relief, Nature -Size : - Generally, the larger and more visible an inclusion, the lower the diamond’s clarity grade. You must also consider the size of the inclusion in relation to the size of the diamond. - One or two of the larger inclusions usually establish the grade. -Number: - When all other factors are equal, the more inclusions or their reflections you see face-up at 10x, the greater the effect on the clarity grade. -diamond’s facets act like mirrors, inclusions might be reflected multiple times making small inclusion is only somewhat easy to see, reflections can make it more apparent. - grades are set by how readily you can see the inclusions rather than by counting them. Locations: - Inclusions are most visible when they’re directly under the table. Inclusions under the crown facets or near the girdle are usually more difficult to see Relief: - Relief is the contrast between an inclusion and its host gem. - a relief high, or more apparent, to low, or less apparent. - Generally, the more an inclusion differs in brightness, darkness, or color from its host, the more visible it is and the greater its impact on the clarity grade. -most diamond inclusions are white or colorless, some are black, brown, dark red, or green. Nature: - Nature refers to the type of characteristic and its effect on the diamond. - Inclusions have more impact on clarity than blemishes. Graders must sometimes refine the clarity grade to a higher or lower level because of nature. - Another factor to consider is an inclusion’s potential risk to the stone. Clarity Grading Procedure: - Step-by-Step Examination: The wedge technique is a useful clarity grading method. This divides the stone into eight sections—or wedges—so you can systematically search for clarity characteristics. - From the pavilion view, each wedge includes a pavilion main facet and two lower half facets, plus one-eighth of the girdle. -Choose a characteristic that is unique and easy to identify. -Increased magnification is sometimes needed to properly identify and document a characteristic. -For grading purposes, clarity characteristics are defined as either callable or non-callable. -A callable characteristic is one that affects clarity , and are visible at 10x mag -A non-callable characteristic is one that does not affect clarity and can therefore exist on a Flawless diamond. These include inclusions and blemishes visible only at a magnification higher than 10x, referred to as “+10x.” GIA Grade Scale: -The clarity characteristics in diamonds come in an endless variety of combinations, so there can never be one single description that automatically describes a grade, so remember that it’s difficult to develop a precise definition of any clarity grade except Flawless. - First, the descriptions of VVS through I list only typical inclusions—not blemishes. That’s because blemishes rarely have much effect on grades lower than IF. -clarity grades describe typical grade-setting characteristics: inclusions or blemishes that establish the grade of a diamond. -remember that the clarity grade is based on the diamond’s overall appearance in a fully corrected 10x loupe -Some industry professionals use variations on the terms “purity” or “quality” to describe the overall clarity of a diamond. -clarity grade is usually based on the largest or most visible characteristics. History of GIA Grading System -In 1952, Richard T. Liddicoat, then president of GIA, started working on a diamond grading system. GIA staffers Lester Bensen and Joe Phillips assisted him, with input from Robert Crowningshield and Bert Krashes. -Unchanged until the 1970s until the IF grade was added. The I3 grade was also added in the 1970s to account for stones with large, obvious inclusions. In the 1990s, the Imperfect grade was renamed Included. Flawless (F): -A Flawless diamond shows no inclusions and no blemishes when examined under 10x magnification. -A diamond can have these features, visible at 10x, and still qualify as Flawless: Extra facets not visible face-up at 10x Naturals entirely confined to the girdle as long as they don’t thicken the girdle or distort its outline Internal graining that’s not reflective, white, or colored, and doesn’t significantly affect transparency Inscriptions that aren’t internal and don’t appear to penetrate the surface when viewed at 10x Mounting features Internally Flawless (IF) -An IF diamond shows only insignificant blemishes—no inclusions—when examined under 10x magnification. Added in the 1970s to describe diamonds that don’t meet the stringent requirements for the Flawless grade. -Normally, the blemishes on an IF diamond can be removed by very minor repolishing. Surface graining is an exception because it usually can’t be polished away. Very Very Slightly Included (VVS1 & VVS2) -VVS diamonds contain minute inclusions that are difficult to see under 10x magnification. -The inclusions in a VVS1 diamond are extremely difficult to see in the face-up position, or they might be visible only through the pavilion. -In VVS2, they’re very difficult to see. (The GIA system uses words like “extremely” and “very” to describe subtle differences in difficulty or ease of viewing inclusions.) Very Slightly Included (VS1 & VS2) -VS stones contain minor inclusions that range from difficult (VS1) to somewhat easy (VS2) to see under 10x magnification. -The grade depends on their overall visibility when considering all five clarity factors. -Typical inclusions that might set the grade include small crystals, knots, distinct clouds, or minor surface- reaching inclusions such as feathers, cavities, or indented naturals. -In very rare cases, a VS stone might contain an eye-visible inclusion. Slightly Included (SL1 & SL2) -SI stones contain noticeable inclusions that are easy (SI1) or very easy (SI2) to see under 10x. All types of inclusions are possible. -Typical inclusions that might set the grade include crystals, feathers, clouds, and twinning wisps. -A stone with an eye-visible inclusion can be graded SI, but in general the characteristics in an SI1 diamond are not usually visible face-up without magnification. You’ll see eye-visible inclusions more often in an SI2 stone. Included (I1, I2, I3) -Diamonds in the I range contain inclusions that are obvious under 10x magnification. -typical of these inclusions:They can be seen face-up without magnification, they seriously affect the stone’s durability, they’re numerous or large enough to affect transparency and brightness -The inclusions in I1 diamonds are usually quite visible to the unaided eye. -In I2, they are easily visible. -In I3, they are extremely easy to see and might affect the stone’s durability. -The size and shape of the diamond is also a factor are also a factor of the grading process Plotting: - A plot is a map of a diamond’s clarity characteristics. The symbols indicate the type, location, relative size, and sometimes the shape of the characteristics being plotted. - Graders use green, red, and black inks to plot clarity characteristics. Each color has its own meaning: Green ink indicates blemishes, with the exception of extra facets. Red ink indicates most inclusions, even those that reach the surface. Red and green inks, used together, indicate cavities, indented naturals, knots, etch channels, and laser drill-holes. Black ink indicates extra facets and, if the stone is mounted, the position of the metalwork. - Graders plot most characteristics on the crown diagram only. But if the plot includes blemishes, they’re plotted wherever they occur. -Another exception is characteristics that break the surface: They’re plotted in every location where they reach the surface. -Characteristics visible only from the pavilion view are plotted on the pavilion diagram. -Plots can come from many different sources. The most common are appraisers, in-store gemologists, diamond dealers, and gemological laboratories. - Many diamond professionals plot only the characteristics that identify the stone, set the grade, or are important in establishing the diamond’s condition. - Some characteristics that aren’t plotted might be mentioned in a report’s comments section. -Naturals and extra facets are often plotted because they’re useful as identifying features. -Often, the fewer clarity characteristics, the more difficult it is to match the plot to the stone. -Whether plotting a diamond or simply reading a plot, the best method for orienting the diamond to the diagram is to use the wedge technique. Reading a Plot: - The grader lists the characteristics in order of importance. When present, laser drill-holes are listed first to ensure clear disclosure of the treatment. -Grade-setting inclusions are listed next, followed by other inclusions in the order of their severity. -Naturals and extra facets are listed last.