10 – Flawless – no blemishes can be found.

9 – VVS-1 – no flaws inside the table. Possible very small internal
flaws outside the table. If any external flaws are present,
must be very minor.

8 – VVS-2 – very difficult to see flaws with 1 0x magnification power
employed.

7 – VS – 1 – flaws readily seen using 1 0x glass but almost impossible
to see when the stone is viewed from from the back.

6 – VS – 2 – the back looking down through the stone.

5 – Sl – 1 – flaws unable to be seen with the naked eyes but quite
apparent using 1 0x magnification.

4 – Sl – 2 – inclusion may include carbon spots or clouds or feathers
underneath the table or larger flaws outside of the table.

3-1 – I-1 to 3 – this is the least valuable group. They are heavily flawed
and the flaws can be determined with the naked eyes. There
are going to be internal flaws inside the table, maybe
clouds, groups of carbon spots, feathers and/or cracks
that can be seen with the eye.

VVS – Very, very, slightly imperfect
VS – Very slightly imperfect
Sl – Slightly imperfect
I – Imperfect

A flawless stone is simply that. No flaw can be found even with the use of a
10x jeweler’s loupe or 10x microscope. As you go down the scale, the VVS-1 may
have one very small inclusion, generally not in the table (which I’ll cover it
later in the file) portion of the diamond but possibly on the edge. Again,
this flaw is seen only from the front and only on using 10x magnification. It
should not be visible to the naked eye.
As we get into VVS-2, there may be more than one flaw wlth magnification but
they’re still extremely small. One small inclusion may be in the table area of
the diamond.
Into the VS grades, the flaws become larger and more prominent than their VVS
cousins. VS2 may have larger flaws or a number of small spots possibly located
in the table of the diamond that group together and are almost considered one
flaw. They are generally in the same area.
When we talk about 10x magnification, this can be in the form of a jeweler’s
loupe which is a fairly inexpensive must-have item for anyone serious about
stones or a step upward which is the two eyepiece (stereo) microscope, which
many jewelers will have on the premises and will let one borrow when perusing
their stones.
It is wise to always make sure that the magnification device employed is 1Ox.
This is the standard and any variation from this will affect the rating of the
stone to a great degree.
Note that flawless VVS and VS rated stones are rated when looking at the stone
right side up with a 1 Ox magnification device. If you pick up a stone that
supposedly falls under one of these ratings and you can see inclusions with
the naked eye, you’re not looking at a stone that is properly rated.
An Sl-1 rated stone will have inclusions that are very obvious under 1Ox
magnification, but should still be borderline visible or not visible when
viewed with the naked eye. The Sl-1 stone may have these borderline visible,
small dots or inclusions in the table or edge of the stone. An Sl-2 rating
will have larger flaws and probably more than one. These will be easily
visible to the naked eye.
In the I grades, the stones can be considered either quite flawed or imperfect.
Flaws are probably inside the table. There may be flaws of more than one
variety, clouds, cracks or groups of black or white carbon spots will be
visible. This last group of stones obviously are the least valuable and the
least interesting for anyone trying to convert from cash to gems and back
again.
Looking backward we can infer several things, the first of which being if you
can spot a number of inclusions without the use of magnification device, the
stone is going to be graded 1, whether l-1, I-2 or l-3 is open to some
subjective effort, but it will be an I rated stone.
If you can’t find flaws with your eye alone but they do become visible when
using a loupe, one can assume that the stone is an Sl rated stone.
The differentiation between an S stone and a VS stone is that in a VS stone
inclusions may not be seen extremely clearly even with the loupe. If the stone
is turned over and laid on the flat front part (the face of the stone – this
is the table) and one views down from the back of the stone where all the
facets come to a point and the flaws are more readily seen here, one can
assume it is a VS-2 or above rated stone.
Note this viewing is done under white light and with the stone loose. It is
very difficult to judge any of the 4 C’s when the stone is mounted. Mounted
stones are not generally considered for investment grade purchases. The stone
should be loose and one should be able to turn it freely.