Below are key elements
that make up a cut and how it affects a gem's appearance.
It refers to the
quality of diamond facets due to the polishing procedure or the blemishes left
after the cutting procedure. Polish elements are situated on the surface and do
not visibly penetrate the gem when viewed at 10x magnification. It is evaluated
on a scale comprising excellent, very good, good, fair, and poor. Most diamonds
have imperfections since craftsmanship mistakes leave polish marks. Hence,
their facets must be carefully polished at the end of the cutting procedure to
diamonds must have excellent smoothness and exceptional regularity to ensure
they do not have burn marks, nicks, wheel/polishing marks, lizard skin, or
abrasions. Nevertheless, the surface of the diamond is anisotropic, implying
that there are harder and softer zones. Thus, 14 dead spots in equally
set-apart three-D areas can cause the facet to be non-polishable. The dead
regions are often situated on the cube and octahedron faces. For fire and
brilliance to not be affected, cutters must ensure that the facets do not
coincide with the dead spots. Artisans can move the facets, which make up the
symmetry, so that they can shine.
Diamond symmetry is
the alignment and appropriate positioning of its facets. A professional artisan
will set each facet proportions that complement the surrounding facets. The
placement must be completed professionally since the facet junction that does
not align will make the stone look uneven. Moreover, the symmetrical quantity
of a perfectly cut diamond will deter excessive carat weight in the profile.
This makes the gem look heavier than it is.
alignment of facets will define the stone's interaction with light. Some light
that hits the stone immediately reflects as a surface stare. A portion of the
light that gets into the stone escapes via the bottom and does not visually
impact the viewer. A very shallow or deep cut will let light leak from the
diamond's internal wall or crown, making many facets dull or dark. As a result,
the general appearance will be less sparkly and brilliant. Conversely,
appropriately placed facets can maximize the amount of light reflecting from
refracts or tabletops and bouncing off the internal walls into an observer's
The visual impacts of
the external and internal interactions with graying light establish the
brilliance of a diamond. Scintillation will be caused by an equal balance of
light and dark spots, creating a clear pattern with no distracting dark
outline. Once the light shows in the gem, it causes fire
as it is dispersed
into a rainbow of shadows-like colors. If the light source, the diamond, or
the viewer moves, the spots of light that spackle (flash) will be noticeable.
The girdle in the GIA
cut grading system refers to the narrow unit separating the pavilion from the
crown and works as the stone's setting edge. It reduces the risk of damage when
adequately thick, comprising 16 hill and 16 valley positions formed by the
final cutting. An optical gadget calculates the average thickness and
percentage using the available formulae. Therefore, the maximum and minimum
verbal descriptions depend on the decisions of GIA lab graders. The thickness
is evaluated as a range from the thinnest to the thickest valley spots. The
maximum and minimum girdle thickness is measured via the non-contact optical
measuring gadget. With the GIA multipurpose gemological reticule and
microscope, you can also measure it. Girdle thickness evaluation depends on
visual observations because the measured outcome results are vulnerable to the
variability inherent in measurement gadgets. This also holds when
differentiating between very thin and exceptionally thin girdles.
Diamond culet size
A diamond culet is a
tiny spot where the latter and the facets meet beneath the pavilion. The pavilion facets are uniformly crafted in many stones at the right angle and close
at the perfect point, leaving no culet. If the pavilion facet does not meet at
an ideal point, the culet will be a rough or polished facet. The existence of
the culet adds to the stone's cumulative number of facets.
A diamond culet can be
rated from extremely large to none. When loose diamonds are sent for
certification, the stone is observed face up to determine the culet's size and
sideways to define its angle. A sharply angled culet is not evaluated as a
culet but as an additional facet. Diamond culet size is expressed as a
percentage relative to the diameter of approved diamonds, with culets ranging
from small to extremely large.
Here is a description of the culet size:
- Note: Since there is no space beneath the pavilion,
light cannot escape the culet and is bounced back. It is a requirement for
well-cut grade diamonds.
- Very small: The culet comprises a tiny opening that is
invisible without magnification. Since light seepage is reduced, it cannot
affect the gem's light performance and sparkle.
- Small: This culet has a noticeable opening that leaks light under magnification. However, the diamond will have incredible
sparkle and high brilliance.
- Medium: A visible opening is noticeable under
magnification, though tiny without it. This will affect the light
performance of the stone since light leaks via the pavilion's center.
- Large: The culet is visibly open and serves as a facet.
Leakage of light takes place, affecting the brilliance of the stone.
- Very large: A vast opening is available in the stone.
You cannot see the brilliance of the stone's cut.
A crown serves as a
window that drives light and defines the brightness of the stone. It also acts
as a prism that disperses light, giving the crown facet size, fire, and angel.
This will help you define the amount of fire the diamond releases. The crown
facet also curvatures light such that what you observe via the crown is a
shifted version of what you can see via the table.
A crown angle is created where the girdle plane meets the bezel facets—the
same as the crown height. Therefore, a higher crown means a greater angle. Most
diamonds have crown angels that range from 25 to 35 degrees. Diamonds with crown angles are more shallow than 25 degrees tend to be bright but more vulnerable to damage than gems with high crowns.
shallower crowns must be placed on mountings to secure the girdle spot, such as
bezel settings, surrounding the gem with a rim of precious metals. Shallow
stones are ideal in jewelry where they are not susceptible to damage. The
craftsman who cuts diamonds from rough attempts to achieve the largest girdle
diameter and high weight retention. Therefore, they are usually cut with
shallow pavilions and crowns and have a large table percentage and thin
The crown angle
compensates for the bending light caused by the initial pavilion. In this case,
the general concept is that the crown angle must be shallow if the pavilion
angle is steeper to compensate for light and vice versa. This implies a crown
angle that maximizes the proper return for any designated pavilion angel.
that the perfect crown angle is 34.5 degrees paired with a 40.75-degree
pavilion angle. Remember that for stone with a 40.7 pavilion angle that
curves light too much, you require a crown angle of 35 degrees to compensate. Similarly, if a stone with a pavilion angle of 41 degrees does not
bend light correctly, you will need a shallower crown angle of 43 degrees to
The pavilion angle
The lower girdle facet
and pavilion are mirrors, and their reflective index defines a stone's ability
to work as a mirror. The reflective index represents the viewpoint that light
is curved at while it gets into the diamond. The angle is vital since stone can
only serve as a mirror when the light hits a perfect angle greater than its
A pavilion angle is
vital in determining whether a diamond is proportioned correctly or if the
stone will require re-cutting. In addition, the table reflection technique
helps identify the pavilion depth/angle when it comes to mounting. In most
cases, a space in the mounting under the culet allows a direct measurement of
the entire depth.
If the general depth
of a pavilion is greater than 63 percent with a shallow crown, it is considered
deep. For instance, visually, you can identify a flat crown by looking at the
stone's side profile and a normal or medium girdle.
40.75 degrees is the
ideal pavilion angle, according to mathematics professionals. Interestingly,
artisans cut the stones at this angle before it was defined. Diamond cutters
claim that beyond 41 degrees, it is too steep. Retailers selling badly cut
stones will lure you by saying that a cliff of 41 degrees is ridiculous.
However, according to physics, there is a critical angle before light escapes.
Hence, what takes place is not a cliff but a smooth transition from stronger
to weaker light as more rays escape.
The aspect to
remember is that the transition happens around 41 degrees. Therefore, unless
you find a super-ideal gem cut at 40.9 degrees, choose
something close to 40.75 degrees. While using light ray tracing, researchers
have found that a pavilion angle of more than 40.5 degrees is exceptionally
shallow and will result in light leakage and obstruction.
Painting and Digging Out
Printing and digging
out refer to the faceting methods for the half facet that influence the stone's
three-dimensional settings. They include the relative position, horizontal
angles, and distance from the center of the stone. The painting and printing methods
are applied to save the stone's weight during the cutting procedure. They get
rid of attachments near the girdle or influence the face-up appearance of the
gem. Note that painting and digging out methods on cut grading are
affected by the virtual distinguishability of the techniques and if the
pavilion or crown or both utilize them.