CLARITY GRADING

Clarity can be defined as the absence of inclusions and internal defects in a stone and corresponds to a relative place of a specimen on the scale "defect-free diamond - diamond with defects". Clarity features are represented by internal defects (inclusions) and external defects. A defect (characteristic) is referred to as internal if it cannot be removed by repolishing without weight loss (even if the defect reach the surface). All other factors being equal, defect-free diamonds are considered the most valuable.

In the Russian system, clarity is traditionally called "defectness" or quality, while the term characteristic is usually applied to defects in the international practice.

The clarity grading is conducted at the tenfold magnification or by the unaided eye. The defects detectable at higher magnifications but not visible at 10x are not considered. When the influence of the defects on clarity is estimated, the size, nature, quantity, distribution, and brightness/color of the internal features (and sometimes external features as well) are taken into account.


The main internal features
  • Solid mineral inclusions of various colors: green olivine, diopside; red garnet; black sulfides or ilmenite; and colorless (diamond inclusion). Other minerals are present more rarely. In diamond grading, the size, color, position, and repeated reflection of the inclusions matter rather than their composition.
  • Pinpoint- a very small inclusion, which usually appears as a point under the loupe. Some specimens contain groups of pinpoints.
  • Needle - a long thin crystal - acicular inclusion.
  • Cloud - hazy or milky zone consisting of a great number of tiny inclusions.
  • Cracks (International systems often use the term "feather")
    • Parallel to cleavage. These cracks are parallel to each other and are orientated in directions of cleavage. They can occur inside a stone and not open to the surface. Under mechanic stress, a stone can be cracked up along the cleavage direction.
    • Cracks resulting from thermal gradient during crystal growth. These cracks may have a chaotic distribution.
    • Tensor cracks. These cracks occur near solid mineral inclusions and originate due to the difference in the coefficient of thermal expansion between the inclusions and diamond. They typically have elongated or disc-like shape
    • Cracks of mixed types are noted.
  • Structural features . appear during diamond crystal growth. Not being a damage or an extraneous object, such features are referred to as structural defects. The defects of this type are often described with such terms as graining, growth lines, twinning wisps and twinning planes. These features may appear as turbid zones, lines, bands, and planes. They can be milky or colored and sometimes influence the total transparency of a stone.
  • Grain center - a small area of concentrated distortion of crystal structure; usually is accompanied by pinpoint inclusions.
  • Nick- a small and shallow pit typically occurring on the girdle edge. Some nicks may have a greater size.
  • Cavity - a large three-dimensional opening on the surface of a polished diamond.
  • Bearded girdle("bearding") - microcracks extending from the girdle into the stone.
  • Bruise - a deformation zone on the diamond surface caused by a blow.
  • Crystal in crystal - a diamond microcrystal inclusion in polished diamond.
  • Knot - a diamond inclusion standing out against the surface of the polished diamond.
  • Indented natural - a natural crystal face which is deepened into the stone.
  • Laser drill hole - a laser-drilled needle-shaped hole, which appears as a pit on the diamond surface.

The main external features
  • Abrasion - smoothing of edges and vertexes mainly caused by careless cutting. Microcracks orientated along the edges are often perceived as white lines rather than sharp edges.
  • Extra facet - a facet present in addition to those required by a given cutting style and which does not fit the symmetry pattern.
  • Natural - part of the original natural diamond surface which is left on the polished stone after cutting.
  • Pit - microopening which often appears as a white point.
  • Polish lines - thin parallel lines left after polishing; thin parallel ridges within one facet caused by the irregularity of the crystal structure; small parallel polished trenches formed by the cutting disk surface.
  • Polishing marks - hazy areas of the stone surface caused by excess heating (superheating) during cutting or polishing.
  • Rough girdle - feathery or cavernous girdle surface, often with microcracks..
  • Scratch - a linear trench, which typically appears as a thin white line (curved or straight).
  • Surface graining - defects and distortions of the diamond crystal structure which reach the surface of the stone and often cross facet junctions.

GIA clarity grading
Symbol GIA Clarity Grades Short Description
IF INTERNALLY

FLAWLESS

No inclusions, and only insignificant blemishes.
VVS1

VVS2

VERY, VERY SMALL INCLUSIONS Minute inclusions that are difficult to see. In VVS1, they are extremely difficult to see, visible only from pavilion, or small and shallow enough to be removed easily by repolishing. In VVS2, inclusions are still very difficult to see. Typical inclusions: scattered pinpoints, faint clouds, slightly bearded girdles, internal graining, and tiny feathers, chips, and bruises.
VS1

VS2

VERY SMALL INCLUSIONS

Minor inclusions ranging from difficult to somewhat easy to see. Typical inclusions: small included crystals and feathers, distinct clouds, and groups of pinpoints.
SI1

SI2

SMALL INCLUSIONS

Noticeable inclusions that are easy (S1I) or very easy (S2I) to see. Inclusions are often centrally located and noticed immediately; that may be eye-visible. Typical inclusions: included crystals, clouds, feathers.
I1

I2

I3

IMPERFECT

Obvious inclusions that are often easily eye-visible face-up; in I3, they may threaten durability. Typical inclusions: large included crystals and feathers.

Clarity grading procedure
  • Preparation (cleaning) of a stone.
  • Face-up examination at 10x magnification. Corrected optics should be applied. Dark field illumination is recommended for determining internal features and reflected light - for external features.
  • Approximate evaluation of the inclusions. Clarity range is usually determined at this stage.
  • Careful profile examination: around the girdle, from different sides (through the crown and pavilion facets). All the features are noted, including size, number, nature, color, and relief.
  • Face-up examination for the evaluation of the total clarity of a stone. If a microscope is used for the study, it is recommended to examine dark-looking inclusions with a loupe. If the detection of an inclusion takes much time, VVS category is assigned. VS - inclusions are easily detected; SI - inclusions are detected immediately; I - inclusions are obvious and are visible to the unaided eye.
  • Differentiation between VVS1 and VVS2; VS1 and VS2; SI1 and SI2; I1, I2 and I3.

Additional recommendations for clarity grading.
  • To distinguish an internal feature from a dust particle, which can be left on the surface, the stone should be slightly tilted or rotated. During the rotation, inclusions move less than dust and external features. Another method is to catch a reflection from the facet which supposedly contains the observed feature.
  • For observation of light inclusions, it is convenient to hold a stone so that the inclusion is seen against the dark background (conversely, dark inclusion - against the light background)..
  • Minor internal features (points, invisible through the table) can be detected by holding the diamond at the girdle with tweezers and orientating it so that the eye direction is perpendicular to the main pavilion facets.
  • When internal features are searched, one should be sure that the diamond bulk is thoroughly examined. The thorough examination is attained by rotating the stone and successive focusing sight on different zones. An expert is free to choose the order of examination most convenient to him.

Representing features on the diagram

The characteristic features of a graded stone should be indicated on the crown and pavilion identity diagrams as well as in the worksheet or certificate. The features are recorded in order to identify the stone, to fix its present state, and to justify its grading. Only those features are noted on which the grades, identification, and description are based. The marks on the diagram usually denote the location of the features, but may not show their actual dimensions.


Symbols and abbreviations in diamond plot
External features
Extra facet u1.gif (182 bytes) EF
Natural u2.gif (189 bytes) N
Abroaded Culet   Abr
Abrasion u18.gif (373 bytes) Abr
Nick u19.gif (166 bytes) Nk
Pit u20.gif (172 bytes)  
Polish lines u21.gif (353 bytes) Pl
Scratch u22.gif (159 bytes) S
Surface Graining u16.gif (164 bytes) Sgr
Bearded Girdle   BG
Internal features
Bruise u4.gif (126 bytes) Br
Chip small u5.gif (138 bytes) Ch
Chip large u6.gif (222 bytes) Ch
Cloud u7.gif (188 bytes) Cld
Feather u8.gif (136 bytes) Ftr
Included crystal u9.gif (159 bytes) Xtl
Internal graining u10.gif (186 bytes) IntGr
Knot u11.gif (192 bytes) K
Laser drill hole u12.gif (146 bytes) LDN
Pinpoint u13.gif (68 bytes) Pp
Twinning wisp u14.gif (202 bytes) W
Grain center u15.gif (193 bytes) CrCnt

Rules for filling diagrams
  • The cutting style shown by the diagram should correspond to that of a graded stone.
  • Naturals bounded by the girdle and all inclusions are marked in the crown diagram, except for those reaching the pavilion surface and those visible only through the pavilion facets.
  • External defects and extra facets are indicated on the sides of the diagram where these features actually occur.
  • The inclusions reaching both crown and pavilion surfaces should be shown on both diagrams.
  • Color of the marks: extra facets - black solid lines; mounting - black hatching; external defects - green; cavities, large nicks, indented naturals, knots, and laser drill holes - red and green; and other inclusions - red.
  • It is recommended to begin with the defects closest to the girdle.
  • Some features may be omitted in copies prepared for a client (certificates) not to overload the diagram.
  • The most obvious (deciding) feature is usually marked in the upper part of the diagram (at "twelve o'clock").

An example diagram with commonly acceptable symbols is shown in figure.