|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
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
- 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
- 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
- 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
||GIA Clarity Grades
|No inclusions, and only insignificant blemishes.
|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.
|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.
|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,
|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
- 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
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
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.