Diamond clarity

From Wikipedia, the free encyclopedia

Diamond clarity is a quality of diamonds relating to the existence and visual appearance of internal characteristics of a diamond called inclusions, and surface defects called blemishes. Clarity is one of the four Cs of diamond grading, the others being carat, color, and cut. Inclusions may be crystals of a foreign material or another diamond crystal, or structural imperfections such as tiny cracks that can appear whitish or cloudy. The number, size, color, relative location, orientation, and visibility of inclusions can all affect the relative clarity of a diamond. A clarity grade is assigned based on the overall appearance of the stone under 10x magnification.

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 fingerprints. 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.

[edit] Inclusions and blemishes

Main article: Diamond flaws

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.

[edit] Inclusions

Clouds
Feathers
Included crystals or minerals
Knots
Cavities
Cleavage
Bearding
Internal graining

The diamond industry uses the term "internal characteristics" instead of "inclusions". For natural diamonds, the "internal characteristics" in the diamond are growth crystals that give the diamond its character and unique fingerprint. When diamonds are graded they are magnified at 10x power.

[edit] Blemishes

Polish lines
Grain boundaries
Naturals
Scratches
Nicks
Pits
Chips

[edit] Clarity grading

[edit] Gemological Institute of America (GIA)

[edit] 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.^[1] In 1953, they released their new system which assessed three aspects of diamonds; make, color and clarity.^[1] 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.^[1] The system at that time contained nine grades, flawless, VVS₁, VVS₂, VS₁, VS₂, SI₁, SI₂, I₁, and I₂.^[1] The I of the I₁, and I₂ grades stood for imperfect.^[1]

During the 1970s 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.^[1] 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.^[1] 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.^[1]

The last change to the clarity grading system took place in the 1990s when the term imperfect was updated to included.^[1]

[edit] The GIA grading system today

GIA diamond clarity grading scale
Category	Flawless	Internally Flawless	Very Very Slightly Included		Very Slightly Included		Slightly Included		Included
Grade	FL	IF	VVS₁	VVS₂	VS₁	VS₂	SI₁	SI₂	I₁	I₂	I₃

The GIA diamond grading scale is divided into six categories and eleven grades.^[1] The clarity categories and grades are:

Flawless category (FL) diamonds that no inclusions or blemishes are visible under 10x magnification.^[2]
Internally Flawless category (IF) diamonds have no inclusions visible under 10x magnification, only small blemishes on the diamond surface^[2]
Very, Very Slightly Included category (VVS) diamonds have minute inclusions that are difficult for a skilled grader to see under 10x magnification.^[2] The VVS category is divided into two grades; VVS1 denotes a higher clarity grade than VVS2. Pinpoints and needles set the grade at VVS^[1]
Very Slightly Included category (VS) diamonds have minor inclusions that are difficult to somewhat easy for a trained grader to see when viewed under 10x magnification.^[2] The VS category is divided into two grades; VS1 denotes a higher clarity grade than VS2. Typically the inclusions in VS diamonds are invisible without magnification, however infrequently some VS2 inclusions may still be visible to the eye. An example would be on a large emerald cut diamond which has a small inclusion under the corner of the table. ^[1]
Slightly Included category (SI) diamonds have noticeable inclusions that are easy to very easy for a trained grader to see when viewed under 10x magnification.^[2] The SI category is divided into two grades; SI1 denotes a higher clarity grade than SI2. These may or may not be noticeable to the naked eye.^[3]
Included category (I) diamonds have obvious inclusions that are clearly visible to a trained grader under 10x magnification.^[2] Included diamonds have inclusions that are usually visible without magnification or have inclusions that threaten the durability of the stone. The I category is divided into three grades; I1 denotes a higher clarity grade than I2, which in turn is higher than I3. Inclusions in I1 diamonds often are seen to the unaided eye. I2 inclusions are easily seen, while I3 diamonds have large and extremely easy to see inclusions that typically impact the brilliance of the diamond, as well as having inclusions that are often likely to threaten the structure of the diamond. ^[1]

[edit] 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 its impact on the clarity grade.^[4]

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.^[4]

[edit] 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.

[edit] Confédération Internationale de la Bijouterie, Joaillerie, Orfèvrerie des Diamants, Perles et Pierres (CIBJO)

CIBJO diamond clarity grading scale
GIA	all stones	FL	IF	VVS₁	VVS₂	VS₁	VS₂	SI₁	SI₂	I₁	I₂	I₃
CIBJO	over 0.47ct^[3]	Loupe clean		VVS₁	VVS₂	VS₁	VS₂	SI₁	SI₂	P_I	P_II	P_III
CIBJO	under 0.47ct	Loupe clean		VVS		VS		SI		P_I	P_II	P_III

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.^[3]

[edit] American Gem Society

AGS diamond clarity grading scale
GIA		FL		IF		VVS₁			VVS₂			VS₁			VS₂			SI₁			SI₂			I₁				I₂				I₃
AGS		0				1			2			3			4			5			6			7			8			9			10

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.^[5]

Clarity grading by AGS standards requires examination using a binocular stereo microscope equipped with adjustable zoom magnification and darkfield illumination. ^[5]

[edit] International Diamond Council (IDC)

IDC diamond clarity grading scale
GIA				FL		IF		VVS₁			VVS₂			VS₁			VS₂			SI₁					SI₂					I₁				I₂				I₃
IDC				Loupe clean				VVS₁			VVS₂			VS₁			VS₂			SI₁					SI₂					P_I				P_II				P_III

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.^[3]

[edit] European Gemological Laboratory

EGL diamond clarity grading scales
GIA	FL	IF	VVS₁	VVS₂	VS₁	VS₂	SI₁		SI₂		I₁		I₂	I₃
EGL USA ^[6]	IF		VVS₁	VVS₂	VS₁	VS₂	SI₁	SI₂		SI₃ ^[7]		I₁	I₂	I₃
EGL India ^[8]	FL	IF	VVS₁	VVS₂	VS₁	VS₂	SI₁	SI₂		SI₃		P₁	P₂	P₃

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.

[edit] 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.^[1]

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.

[edit] 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.^[1]

[edit] Number

The second clarity factor which is assessed is the number of clarity characteristics. Generally the more characteristics the lower the clarity grade. This assessment is made by judging how readily they can be seen, not by the actual number of characteristics. ^[1]

[edit] 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.^[1]

In addition the position of large feathers, knots and included crystals positioned where they extend to the girdle or crown of the stone, affect 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.^[1]

[edit] 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.^[1]

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.^[1]

A diamond's external characteristics can be an; abrasion, natural, nick, pit, polish lines, polish mark, scratch, surface graining, or extra facet.^[1]

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.^[1]

[edit] 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.^[1]

[edit] Rarity and value

Diamonds become increasingly rare when considering higher clarity gradings^{[citation needed]}. 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^{[citation needed]}, although visible inclusions can sometimes be hidden under the setting in a piece of jewelry. The most expensive gem diamonds fall within the VS and SI grades with FL, IF, and even VVS stones commanding significant premiums^{[citation needed]}, while I stones are shunned by most buyers^{[citation needed]}. FL and IF stones are sometimes referred to as "museum quality" or "investment grade" to denote their rarity^{[citation needed]}, although the term "investment grade" is misleading as diamonds have historically been illiquid and questionable stores of value.

[edit] Clarity enhancement

Main article: 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.

GIA, as a matter of policy, does NOT certify clarity-enhanced diamonds. If you see a GIA Diamond Report with the words "clarity enhanced" or "fracture-filled," it is surely a counterfeit report.

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.

[edit] See also

[edit] References

^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ ^o ^p ^q ^r ^s ^t ^u ^v ^w "Diamonds and Diamond Grading" course material - Book 11, Grading Clarity, Gemological Institute of America, 2002
^ ^a ^b ^c ^d ^e ^f What is the GIA Clarity Scale for diamonds? GIA website, accessed December 7 2006
^ ^a ^b ^c ^d Pagel-Thielsen, Verena G.G., F.G.A. Diamond Grading ABC: The Manual Rubin & Son n.v., Antwerp, 9th edition, 2001, ISBN 3-9800434-6-0.
^ ^a ^b Diamond Grading: Lab Manual Gemological Institute of America, Carlsbad, 2004
^ ^a ^b The AGS Way: Diamond Grading Standards American Gem Society, 1999
^ EGL USA clarity scale
^ Tashey Thomas E. Jr, Roskin Gary A. European Gemological Laboratory Defines SI3 Cornerstone, Summer 1992 – A publication for Accredited Gemologist Association, accessed online February 18, 2007
^ EGL India clarity scale

Categories: Diamond