Tag Archives: stone

Carat weight diamond grading

The fourth and final C in evaluating a diamond for purchase is the carat
weight. The term carat is a reference to biblical times when diamonds were
compared against a carob bean because carob beans tend to have a uniform size
and weight. One carob bean became the equivalent of one carat. The carat is
still the primary unit of diamond weight used today. However, a carat is
further broken down into 100 sub units called points. One point equals 1/100
of a carat.
When you buy diamonds it is often mentally economical to break the price of
the stone down to a per carat basis. A rather crude example would be if you
were buying drugs you would break the price of a kilo down into a gram weight
to establish what you are actually paying per unit. The same is true in
diamonds. You should divide the weight of the diamond into the price to get
the carat weight.
The next thing to realize is that carat weights do not follow a linear
progression in terms of price. There are certain man-made break points in
diamond pricing. The first break is at .50 (1/2) of a carat. The second break
is at 1 carat and then succeeding breaks occur at each carat thereafter.
These breaks, although arbritrary, are valid and a diamond that is .52 of a
carat will cost considerably more than a diamond that is .44 of a carat. A
diamond that is over 1 carat, say 1.03 carats, will cost considerably more
per point or per carat than would a diamond that is .94. Because this break
is so critical, one should always see a diamond weighed in front of one on a
scale that has been verified by using an accurate unit of measure. In other
words, put a one gram weight on the scale and see if it actually reads one
gram.
Because of the price involved, these break points are quite important and one
does not want to pay the price differential for over a 1 carat diamond for one
that’s actually a couple points under. When it comes time for resale, the next
buyer will not be so generous in his consideration of the weight.
These price breaks are very substantial and are one of the few things in
diamond selling that is not subjective. As such they are quite evident in all
diamond sales. The difference per carat weight in a diamond that weighs from
1 to 2 carats may be as much as $1,000 per carat or more, on a 2 to 3 carat
diamond. This holds true on a 3 to 4 carat diamond also. One could expect to
pay not $1,000 more but $1,000 per carat more. This tends to increase as one
gets into the heavier weights and good grades of stones because the stones
become much rarer. It is much easier to find small good stones than it is to
find large stones of the same quality.
Wholesalers and for that matter, diamond retailers, buy their diamonds on a
per carat basis and if you are going to buy from anyone in the business, you
should consider the stone in that same light.
It is practically impossible to quote diamond prices in a paper like this
because they are subject to change and market fluctuations. Retail diamond
prices are also subject to seasonal conditions and one will find that holidays
and gift giving times such as Christmas tend to bring about severe prices from
retail outlets while the spring and summer months will often evoke a more
favorable estimate from a retailer who needs to make his rent that month.
Wholesale diamond prices should not change too much due to seasons or gift
giving times. Wholesale prices will vary when the market demands exceed supply
and also tend, as with gold, to function somewhat independently and opposite
of “soft” currency such as the dollar.
The price one pays is determined by how much the seller wants to sell the
stone and how much the buyer wants to buy it. Obviously in certain situations,
stones are cheaper than they would be in a high markup area such as with a
retail jeweler.
A stone may come with an appraisal sheet from one of the two gemological
societies recognized in America. This sheet, as we have seen, details a number
of qualities about the stone and will establish an appraised price. A couple
things one should be aware of about appraisals; the first is that they’re
invalid generally.
Appraisals are an instrument designed for insurance companies to establish a
possible price on a diamond that includes a number of factors such as increase
in value during ownership. The appraisal sheet will be inflated over the value
of the diamond. One never expects to pay full appraisal price for a diamond
and if one does, the term “saw you coming” falls quite aptly into place.
Appraisals also vary from person to person even with accredited gemologists.
The same stone can bring about two entirely separate appraisals that may
differ in value by hundreds or even thousands of dollars. Again, the appraisal
is a piece of paper that allows the insurance company to set a value on the
stone, not that the insurance company will necessarily pay off the appraisal
at full price either.
One cannot make a living by buying diamonds, having them appraised and then
reporting them to the insurance company for too long.
Appraisals, on a very general basis, tend to be nearly double the price that
a stone will actually sell for. This is a very wide statement and some
appraisals will, of course, be closer to the actual value of the stone than
will others.
Appraisals cost money and if you are good enough to sell the qualities of the
stone after a little bit of practice, your own word and your own peace of mind
will be more valid than a piece of paper. You are buying a piece of paper
that someone else may not want to buy.
One should actually consider that one is buying the stone, not a piece of
paper telling one how valuable the stone is. This could be compared to buying
a car because the owner wrote an article about how exciting the car was.
Needless to say one should base the actual purchase price on the vehicle
itself…
Reasons for getting an accredited appraisal are having the stone you want
insured, or when you go to sell the stone, having an appraisal that verifies
the stone’s quality to an unsophisticated buyer and that lists the price
considerably higher than you actually expect to get for the stone, which may
help sell the stone.
This is a nice line of thinking as long as you are the seller and not the
buyer. This is a buyer beware type of business and you should know what you’re
getting and should take all safeguards possible to insure you’re getting what
you think you are. If you’re buying in a slightly dubious situation and
perhaps are not as concerned with the stone’s pedigree as some people would
be, you should be prepared to never see the seller again and live or die on
your evaluation of the stone, not a piece of paper from an appraiser.
It should also be pointed out that in certain situations one would not want to
take a stone in to an appraiser. I will leave this to the imagination of the
reader.
Although appraisals are intended for an insurance company’s benefit, one
should realize that if an insured stone is stolen or otherwise destroyed, the
insurance company may want additional information regarding the purchase of
the stone along with an independent appraisal. There are exceptions to this
rule. If this stone was a gift or was left to one in an estate, obviously an
appraisal becomes the primary instrument of value determination and, as such,
is extremely useful to have on hand.
As a sidebar here, there are ways of destroying or damaging a diamond, even
though a diamond is one of the hardest materials known to man. As previously
pointed out, they are brittle. If you strike a diamond with a hammer, you’ll
dissolve it into useless industrial dust. If you touch a diamond to an
acetylene torch of significant temperature, you will observe an extremely
interesting and costly phenomenon where the diamond turns back into the same
black carbon that it came from.
Graphite, in other words. Once this happens the only recourse is to hope the
diamond was large enough to burn in the furnace and get some heat because
there is no way of changing it back quite as readily to its crystalline form.

Cut grading diamond

Bear in mind also that a good diamond cutter can cut a colored stone in order
to make it appear whiter than it is WHEN THE STONE IS MOUNTED by doing a
shallower cut that’s more spread on the point where the facets come together.
This will make the stone appear less yellow, again only after it’s mounted.
This is another reason one should never judge a stone that is in a mounting
of any sort.
The cut of a brilliant diamond may be the most singular important consideration
in buying a stone within a set price range. Unless one is an expert and feels
his knowledge is good enough to override general public consideration, there
is only one cut to consider and that is the “brilliant” cut. Brilliant cut is
a modern cut that is a completely round stone designed with 58 facets to
maximize light reflection and “fire” within a diamond.
There are a lot of stones still around which have what is known as a European
cut. This cut was done in the 1920′s and before and does not compare in value
to the modern brilliant cut. The old cut or European cut stones were cut
before exact ratios and angles were established and understood by the gem
cutting society and, as such, do not maximize the reflecting and refraction
qualities of the stone. European cut stones such as those purchased at pawn
shops and estate sales, are much harder to resell and do not offer the
liquidity of a brilliant cut diamond.
There are other popular modern cuts such as the marquise, the oval and the
pear which attract some buyers when designed for jewelry, due to their unique
appearance. These cuts do not reflect as well as the brilliant cut and are
rarely seen in investment quality jewelry. Again, the fancier cuts will be
on the average much harder to sell (definitely harder to sell to a dealer)
than is the round brilliant cut stone.
Fancy cut diamonds have fewer angles cut to what is known as the “critical
angle” and, as such, cannot be as brilliant as a round cut stone. The fancier
a stone is, the more it differs from a brilliant cut, the greater the loss in
light reflection will be.
Another phenomena to be aware of in fancy cut stones such as pear shapes or
marquise shapes, is something called the bow tie effect. This is a dark,
cloudy area across the upper portion of the table on these stones. It is a
quality inherent in the cutting and looks like a cloudy bow tie across the
reflecting portion of the table. This obviously lowers the value of the stone
considerably and, if one is thinking about a fancy cut stone, this effect
should be taken into consideration.
Fancy cut stones have only two bottom facets as opposed to the eight found in
round cut stones to reflect the light back. While they still may appear to be
fairly brilliant, the refraction, the fire of the stone, will suffer
critically. This loss progresses from the marquise cut through the straight
cuts such as the emerald cut diamond. These straight cut stones suffer a great
light and fire loss and are not nearly as valuable as the same stone would be
cut in a brilliant cut.
An uncut diamond is normally sawn or split into two or more stones as decided
by the diamond cutter. It just takes a simple error here to completely ruin a
valuable stone and turn it into nothing but dust. Now you can understand the
hypertension rate among diamond cutters and airport controllers…
Once a rough diamond is split, the diamond cutter then decides how the stone
will be laid out and cut. This operation means that a certain portion of the
diamond will be ground off and lost and so this cut plan becomes an important
step in finishing the final stone.
The first step taken by the diamond cutter is to girdle the diamond. This
process of girdling establishes the size of the stone and puts a “waste” on
the stone (see the diagram). If a stone is poorly girdled, it will not appear
completely round when viewed with the jeweler’s loupe or microscope. A round
brilliant cut stone should be perfectly round and symmetrical.
Other mistakes in girdling will produce flaws that manifest themselves as a
razor thin girdle which is prone to chipping or breaking (even though diamonds
are extremely hard, they are brittle and can be chipped or shattered in thin
areas). A too thick girdle takes away from the brilliance and fire of a stone
and indicates a poor job on the part of the diamond cutter.
A diamond cutter cuts (in a brilliant cut) 58 facets all done on exact angles
in exact positions in order to let the diamond reflect as much light as is
physically possible. The brilliant cut stone has 16 facets on top and 16
facets on the bottom that reflect the light and give the stone its cut. Each
facet is cut on a unique angle and is exactly straight when viewed with other
facets in order to maximize light reflection.
When you view a brilliant cut stone, around the table of the stone you’ll see
the kite and the topmain facets. These facets are the areas that allow the
light to come through to the viewer. Beneath these you have eight star facets
and then 16 upper girdle facets before you reach the girdle itself. Beneath
the girdle you have an additional 16 lower girdle facets. All these ancillary
facets contribute to the light reflection through the kite and top main facets
and the table portion of the stone.
What is the advantage of the 58 facet brilliant cut stone? What does one
expect to see when viewing a diamond? There are two qualities that make a
diamond attractive to the eye. The first one is known as life and indicates
the amount of light that is reflected back from the diamond to the viewer.
The second quality is known as fire, which is an indication of the amount of
refraction from the facets and split into colors as in a prism effect.
Besides the 58 facets, a number of other factors contribute to the perfectness
of a brilliant cut stone. The stone’s table should be 53% of the area of the
stone. While the ratio between the depth of the stone or the length of the
stone if you view it from the side, to the spread of the stone which is the
maximum diameter of the girdle, this ratio should be 60% depth to spread.
The angles on a stone must be cut exactly to critical angles. Any deviation
will produce a less than perfect reflection of the light waves entering the
stone. A jeweler will have special gauges to measure these angles. These
gauges are available but they are expensive. Or one can buy a loupe that is
marked with angle markings.
When angles are viewed through this loupe, they can be accurately measured .
The first measurement to take is the degree of the angle from the table to the
girdle of the stone. This is known as the top critical angle and should be 34
1/2 degrees. Underneath the girdle, the bottom angle from the girdle to the
point of the stone is also a critical angle and should be cut at 40 3/4
degrees. A further measurement is that the girdle should be about 1% as thick
as the diameter of the stone, although this is not quite as critical as the
other measurements and can be judged by the eye after a bit of practice.
A stone which is not cut with the critical angles in the right degree, will
either be shallow cut or deep cut and will not reflect the light back through
the center of the stone (the table of the stone) with the same brilliance as
a stone that is cut to the correct angles.
If the stone is shallow cut, the light will reflect off the edges of the stone
but not through the middle. If it is cut too deeply, the center of the stone
will appear to be dark and it is called “heavy.” In the past some cutters cut
the upper angles at a less than 30 degree cut. This “spread cut” helps hide
deficiencies in a stone but makes the girdle angles sharp and likely to be
broken or chipped and the stone is not as valuable as a normally cut stone.
If the correct tool for sizing angles is not available, one can estimate that
if the table appears to be larger than it should, and the width to height
(that is the depth spread ratio) is below 60%, one can assume that the
critical crown angles are shallow.
It is possible to polish a diamond to a high degree to compensate for shallow
or deep cut angles at first glance and make the stone appear to be more
brilliant than it, in fact, is. If the stone is chosen for investment quality,
a measurement of these angles is almost essential .