How
to Value a Diamond:
When considering purchasing a commodity as precious as diamonds,
it is important to know the factors affecting the true value of a given stone.
Most "Jewelers" will promote carat weight as the primary
determination of value when, in fact, cut, color and clarity can all have greater influence on the value of a loose diamond
than carat weight alone.
The
Gemological Institute of America (GIA) has taken great strides in developing a
grading system to standardize value in diamonds. These diamond-grading
standards are applied to cut, color and clarity by professionally trained
gemologists worldwide. Having noted that, it is also important to point out
that there are other International or universal grading systems that are as
effective and almost as wildly used as the GIA grading system. The basic 4 Cs
that is used in determining the value of a diamond are as follows:
1. Carat Weight
Carat
is often confused with size even though it is actually a measure of weight. One
carat is equivalent to 200 milligrams. One Carat can also be divided into 100 points. A 0.75-carat diamond is the same as 75 points
or a 3/4-carat diamond. Larger diamonds are found relatively infrequently in
nature and are therefore more valuable.
Please
note that a 1-carat diamond doesn’t cost exactly as 2 (0.5 carat) diamonds.
Since the larger diamonds are found less frequently in nature, a 1-carat
diamond is much more expensive than twice as much as a 0.5 carat diamond.
Assuming cut, color and clarity remain constant.
The
word Carat is derivative of the world carob. Carob sees are surprisingly
similar in weight to one another; thus, they were used in ancient times as the
reference tool to measure the weight of a diamond. One carob seed equaled
1-carat. Please also note that carat (“ct”) is not Karat (Kt) which refers to
the purity of gold.
2. Cut
Just like water, glass or any other transparent medium, the
density of diamond will "bend" light at a specific angle as it passes
through. In the 18th century, a
mathematician named Marcel Tolkowski developed a
mathematical model that calculated the behavior of light as it passed through a
diamond. He used this model to determine the optimum angles of cut that would
reflect and refract the greatest amount of light back out the top of a diamond.
These "Ideal" proportions are alternately referred to as "Tolkowski Cut", "GIA Class 1 Cut" and
"AGS 0 Cut". True "Ideal" proportions have only been
calculated for Round Brilliant Cuts. They are listed in the Table
and Depth Percentage Chart
below, as well as the best or "preferred" cut proportions for the
other shapes.
Table and Depth Percentage are two critical
measurements for loose diamonds. The angles of cut will affect a diamond's
natural ability to both reflect and refract light, that is, the diamond's
ability to virtually explode with brilliance. If a diamond is cut too deep,
light leaks out the sides, brilliance is lost and the center of the diamond
will appear to be dark. If a diamond is cut too shallow, light leaks out the bottom
and the diamond appears watery, glassy and dark. If the proportions are good,
the sides and bottom of the diamond will all reflect their light back out to
the top of the diamond, which creates the brilliance diamonds are famous for.
The Table percent is
the width of the top facet of the crown compared to the diamond's total width.
Table width between 53% and 64% are considered Preferred in Round Brilliant Cut
diamonds.
The Depth percent is
the total depth or height of the diamond compared to the total width. Depth
measurements between 58% and 63% are considered Preferred in Round Brilliant
Cut Diamonds. The Preferred range for these measurements will change as the
shape changes, i.e. a Marquise cut diamond will have different ranges for
Premium Table and Depth percentages. The following table shows the Ideal ranges
for depth and table for Round Brilliant diamonds as well as the Preferred ranges for Rounds and all other shapes:
Table and Depth Percentage Chart:
|
IDEAL SHAPE |
|
|
|
Round
Brilliant |
59% to 62.6% |
53% to 57% |
|
PREFERRED CUTS |
|
|
|
Round
Brilliant |
58% to 63% |
53% to 64% |
|
Marquise,
Oval, Pear |
58% to 66% |
56% to 64% |
|
Emerald,
Radiant |
59% to 69% |
60% to 69% |
|
Princess |
60% to 75% |
60% to 79% |
|
Heart Shape |
55% to 65% |
51% to 65% |
Naturally, diamonds with measurements within those ranges will
be more expensive than diamonds with measurements outside those ranges. You
need to balance that decision yourself. A few %'s one way or the other are minimal.
Besides Table and Depth Percentages, there are several other
minor grading factors that combine to affect the diamond's beauty and value.
Polish measures the quality of finish on the
facets.
Symmetry refers to the proper alignment of the
diamond's sections, the proper shape for the cut (circular for round
brilliants, rectangular for emerald, etc.) and the uniformity in size and
angles of similar facets.
Both Polish and Symmetry are rated as: Excellent (EX), Very
Good (VG), Good to Very Good (GVG), Good (G), Fair to Good (FG), Fair (F), Fair
to Poor (FP), or Poor (P). An excellent rating is very rare. The Very Good,
Good to Very Good, and Good ratings are common and desirable. They will also
affect the price, though not as much as Table and Depth.
Fluorescence, normally blue, can naturally occur in
diamonds and becomes visible under Ultra Violet light. Fluorescence can be
clear or cloudy. Cloudy Fluorescence is undesirable. Fluorescence can be rated
as: Nil or None, Very Faint, Faint, Medium, or Strong. Nil to Faint
Fluorescence will have negligible impact on a diamond. Medium to Strong Blue
Fluorescence can actually be an asset in Color Grades I, J, K, L and up as it will tend to enhance the diamond's brilliance
and make it appear "whiter".
The Girdle is the spacing between the upper and lower portions of
the stone. Girdles can be rated from extremely thin to extremely thick. Extreme
grading should be avoided. The girdle finish can be natural, polished of
faceted. Finer diamonds will normally have faceted girdles.
The Culet size refers to the smallest polished
facet at the very bottom of the diamond. Avoid large or chipped culets.
Unfortunately, these ideal cut diamond
proportions require a great amount of the diamond to be cut away, minimizing
the remaining carat weight. Since loose diamonds are priced and sold by carat
weight, this creates a natural contradiction in priorities: cut quality or
carat weight? A properly cut diamond will virtually explode with dazzling
brilliance and color. An improper cut, often for the sole purpose of leaving
added carat weight, will leave dark, glassy or watery looking areas in the
diamond. Less than 10% of all Round Brilliant diamonds qualify for true Ideal
Cut, and only about 20% of all loose diamonds qualify as Preferred Cut. That
leaves 80% of the market cut with carat weight as the priority as opposed to
brilliance.
Diamond Cutting Tools and Machines
3. COLOR
Diamonds vary in color from colorless to slight tones of yellow
or brown. Colorless diamonds are most brilliant, most rare and most valuable.
The following scale shows the GIA loose diamond color rating systems. The D-J
ratings are among the most desirable.
Color
Chart
|
||||
|
Colorless |
Near Colorless |
Faint Yellow |
Very Light Yellow |
Light Yellow |
|
D E F |
G H I J |
K L M |
N O P Q R |
S T U V W X Y Z |
Truly colorless diamonds such as D are
extremely rare and consequently extremely valuable.
4. CLARITY
Practically all diamonds contain naturally occurring internal
characteristics called inclusions. The size, nature, location and number of
inclusions determine a diamond's clarity grade and affect its value.
The following scale shows the GIA
diamond clarity grading:
|
Clarity Chart |
|||||
|
FL |
IF |
VVS1 - VVS2 |
VS1 - VS2 |
SI1 - SI2 |
I1 - I2 - I3 |
|
Flawless |
Internally
Flawless |
Very Very Small Inclusions |
Very Small
Inclusions |
Small
Inclusions |
Imperfect |
FL: Flawless -- no internal or external
inclusions of any kind visible under 10x magnification to a trained eye, the
most rare and expensive of all clarity grades
IF: Internally Flawless -- no internal
inclusions visible under 10x magnification to a
trained eye, but there may be some tiny external irregularities in the finish
VVS-1: Very Very Slightly Included 1 --
usually just one tiny inclusion visible only to a trained eye under 10x
magnification
VVS-2: Very
Very Slightly Included 2 -- tiny inclusions visible
only to a trained eye under 10x magnification
VS-1: Very Slightly Included 1 -- very small
inclusions visible with 10x magnification
VS-2: Very Slightly Included 2 -- several very small inclusions
visible with 10x magnification
SI-1: Slightly Included 1 -- small inclusions
visible with 10x magnification
SI-2: Slightly Included 2 -- several small
inclusions visible with 10x magnification
SI-3: Slightly
Included 3 -- inclusions that may be visible to the naked eye for a trained
observer
I-1: Included 1 -- flaws that are visible to the naked eye
I-2: Included
2 -- many flaws clearly visible to the naked eye that also decrease the
brilliance
I-3: Included 3 -- many flaws clearly
visible to the naked eye which decrease the brilliance and compromise the
structure of the diamond, making it more easily cracked or chipped
NOTE: We feel that diamonds of clarity grades
I-1, I-2 or I-3 (Imperfect 2 and Imperfect 3 as described by GIA) are not ideal
as a representation of the bond of eternal love. Therefore, we do not recommend
diamonds of these clarity grades for engagement rings. We can provide you such
diamonds upon request only.
Additional Information about Diamond
Diamond Properties
Technical Information:
Colors: Colorless,
Yellow,
Extremely rare
colors: Red, Blue, Green, and
Purple.
Chemical
composition: C - carbon
Crystal
Structure: Cubic - isometric
Hardness: 10
Specific Gravity: 3.52
Note: Size
is relative to specific gravity, its density. A 1.00ct opal would be much
larger than a 1.00ct diamond. A 6.5mm sapphire of equal cut would be 1.14ct.
Refractive Index: 2.42
- singly refractive.
Dispersion: .044
Fluorescence: Photoluminescence
- A natural occurrence of some diamonds, the emission of a visible glow
stimulated by invisible wavelengths, UV light. Diamonds can fluoresce
any color; the most common color is blue.
The strength of fluorescence is described
in the following terms:
None: also known as inert.
Faint: occurs around the girdle's edge
Moderate: glows, but not strongly
Strong: the whole stone glows brightly
Other Varieties: Bort
Poorly Crystallized,
Inferior color.
Carbon ado
Gray to black to
opaque in color.
Used as abrasives in cutting diamonds, and bits for drilling
rock.
Scientists
have divided diamonds into 2 groups:
Type I - gem quality stones are characterized by their absorption of the
ultra-violet below about 3000A and by an absorption band in the infrared.
Type II - transmit ultra-violet to about 2250A, and this group is further
divided into 2 sub-groups Type II a, Type II b. The latter being the
interesting as natural blue-colored stones and is electro-conducting.
THE SCIENCE:
Diamonds are the crystalline of carbon, transformed
by extreme heat and pressure. There is only one natural environment in which
diamonds can be formed, and that is in molten rock from 75 to 120 miles below
the earth's surface.
Diamond crystals then surface in volcanic eruptions.
The trip is precarious: the crystals may revert to free carbon atoms, vaporize
into carbon dioxide, or turn into graphite (the common "lead" pencil
ingredient) along the way. The only way diamond preserves its original form is
through a rapid cool-down near the earth's surface. With a few unusual
exceptions, the only kind of rock that can bear diamond to an accessible depth
is called kimberlite, after the town of
Diamonds form under large, stable,
cooler plates of earth called "cratons."
Dry earth diamond sites are known as "primary deposits" because they
lead directly down to the stones' subterranean birthplace. But it is only since
the South African diamond rush in the l870's that diamonds have been mined from
dry earth -- for thousands of years diamonds were only sought in riverbed sands
and gravel.
Alluvial diamond sites are called
secondary deposits. Massive geological shifts, and the
movement of glaciers and water can bear diamonds thousands of miles from their
original underground source. Most of the world's finest diamonds were
discovered in secondary deposits, in the famous riverbed mines of
Diamonds can also travel to marine
deposits. At present, one of the richest of the world's diamond sources is
found on a l00-mile stretch of beach south of
Be Aware Of Diamond Treatments:
Yes, it is
true, diamond can be treated and the following is provided for your
Information:
Diamond
Treatments
Some treatments can provide a solution to the problems of a
diamond, making it more valuable. Your jeweler should disclose any treatments
or enhancements, ask if the diamond you are considering is treated. Most
reputable jewelers will disclose this fact.
Clarity
Enhanced, Fracture Filled Diamonds
The clarity enhancement process was developed in 1982 by Israeli
inventor and diamond cutter Zvi Yehuda,
and involves filling cracks in diamonds with molten glass to improve their
clarity. Only diamonds with small cracks can be treated, and this method
improves diamonds clarity by one grade without affecting the color or weight of
the diamond.
Not all clarity-enhanced diamonds are the same, nor do they all
come with a guarantee. Some companies use bromine to enhance their diamonds
because the process is cheaper than using glass. Diamonds treated with bromine
have been known to discolor and cloud with exposure to the ultra violet
radiation found in sunlight.
Laser
Drill
Since the 1970's lasers have been used to burn minute holes in
diamonds to reach dark inclusions and bleach them with acid so they are less
visible. Some are then filled with a glass like substance.
Irradiated
Diamonds
The affordable Fancy colored diamond. Artificially colored
by electron bombardment. The coloration is permanent.
Painted
for color
Diamond can be
painted to offset a yellow tinge.
Coated
Diamonds
Some diamonds are coated to enhance or improve their color. A
coated diamond might go undetected for years if the diamond is not examined by
an experienced grader, gemologist.
If you decide to buy a diamond that has been treated, and later
that item needs to be cleaned or repaired be sure you disclose the type of
diamond treatment to your jeweler to avoid any damage to your jewelry or
misunderstandings. Find out more about treated diamonds to help you decide if
this is a choice you really want to make.
Notice:
We do not sell, or deal with diamonds
that have had any of the above red treatments, or any
treatment at all.
Diamond Look a Likes:
The following
may have the appearance of natural diamonds, but do not share the same
physical, optical and chemical properties. The most common simulates include
colorless glass, white sapphire, white topaz, synthetic cubic zirconia and, synthetic moissanite.
Info:
|
Diamond Simulate Types |
Synthetic Cubic Zirconia |
Synthetic Moissanite |
Real Diamond |
|
Hardness: |
81⁄2 |
91⁄4 |
10 |
|
Toughness: |
Good |
Excellent |
Good |
|
Specific Gravity: |
5.65 - 5.98 |
3.21 |
3.52 |
|
Dispersion: |
0.060 |
0.104 |
0.044 |
CZ is actually the better diamond simulate even though it is
softer than Moissanite. Both of these stones can not
compare to diamonds natural inherent beauty or durability.
Look for:
Synthetic Cubic Zirconia: Hazy
transparency, gas bubbles "stingers",
read through, and fogs up using the Huff Test.
Synthetic Moissanite: Double refraction is detected through crown facets. Silk
like inclusions. High dispersion (the fire) unlike diamond.
Synthetic Diamond: shares
the identical, optical, chemical, and physical properties of natural diamonds.
Detection of synthetic diamond is very difficult. Testing procedures involve
evaluation of magnetic properties, fluorescence patterns and the identification
of diagnostic inclusions.
Moissanite: Silicon
Carbide - SiC
Natural occurrence is extremely rare first found as tiny
crystals in the analyzes of the
Zircon: Zirconium
silicate - ZrSiO4
Often mistaken for Synthetic Cubic Zirconia
History of Diamond:
Discovery:
The first river-bed (alluvial) diamonds were probably
discovered in
Throughout much of history, diamonds were mined from
the sand and gravel surrounding rivers. But in
Cutting:
The cutting of diamonds into the complex facetted
forms we now associate with these gems is actually a relatively recent
practice. For centuries, rough diamonds were kept as talismans, and often not
worn at all, though natural octahedral (eight-sided stones) were sometimes set
in rings. A Hungarian queen's crown set with uncut diamonds, dating from
approximately l074, is perhaps the earliest example of diamond jewelry. We know
that the royalty of
The earliest record of diamond polishing (with
diamond powder) is Indian, and probably dates from the fourteenth century.
There are also contemporary references to the practice of diamond polishing in
Diamond
Routes and Centers:
Indian
diamonds reached
After Spanish attacks on