Diamond clarity
Large cracks close to or breaking the surface may reduce a diamond's resistance to fracture.
Features resulting from diamond enhancement procedures, such as laser lines, are also considered inclusions or blemishes.
In 1952, Richard T. Liddicoat, along with Marquis Person, 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".
[2] They took terminology used in the industry at the time and refined the definitions to produce a clarity scale by which diamonds could be consistently graded.
This change was made in response to a growing number of diamonds of very low clarity being cut.
The GIA Laboratory uses as standard equipment binocular stereo microscopes which are able to zoom to higher magnifications.
The grader views the diamond for the first time through the table, studying the culet area of the stone for inclusions.
The grader first decides the clarity category of the diamond: none (FL, or IF for a blemish), minute (VVS), minor (VS), noticeable (SI), or obvious (I).
The World Jewellery Confederation developed the International Clarity Scale for grading diamonds.
[7] Clarity grading by WJC standards is by examination using a 10× achromatic, aplanatic loupe in normal light.
[8] Clarity grading by AGS standards requires examination using a binocular stereo microscope equipped with adjustable zoom magnification and darkfield illumination.
IDC loupe clean stones that have external blemishes have notations made on the grading report.
IDC clarity grading is by examination using a 10× achromatic, aplanatic loupe in normal light.
Because GIA and EGL use the same nomenclature, but apply the standards differently, purchasers of diamonds can be easily confused or mislead.
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.
Larger characteristics are typically more noticeable under magnification, thereby placing the diamond into a lower clarity grade.
Inclusions that are judged to pose at least a moderate risk of breakage to the stone are graded in the Included category.
[2] An internal characteristic of a diamond may be classified as a(n): bruise, cavity, chip, cleavage, cloud, crystal, feather, grain center, indented natural, internal graining, knot, laser drill hole, needle, pinpoint, or twinning wisp.
The most expensive gem diamonds fall within the VS and SI grades with FL, IF, and even VVS stones commanding significant premiums.
FL and IF stones are sometimes referred to as "museum quality" or "investment grade" to denote their rarity[according to whom?]
although the term "investment grade" is misleading as diamonds have historically been illiquid and questionable stores of value.
Reputable companies often provide for repeat treatments if heat causes damage to the filling.
