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Roughly 49% of diamonds originate
from central and southern Africa, although significant sources have been discovered in Canada, India, Russia, Brazil, and Australia.
The 4 C's & Valuation:
Most gem diamonds are traded on the wholesale market based on single values for
each of the four Cs:
For example, knowing that a diamond
is rated as 1.5 carats, VS2 clarity, F colour, and an excellent cut as "round brilliant", is
enough to reasonably establish an expected price range. More detailed
information from within each characteristic is used to determine actual market
value for individual stones. Consumers who purchase individual diamonds are
often advised to use the four Cs to pick the diamond that is "right" for them.
Other characteristics not described by the four
Cs influence the value or appearance of a gem diamond. These characteristics
include physical characteristics such as the presence of fluorescence, as well
as data on a diamond's history including its source and which gemological
institute performed evaluation services on the diamond. Cleanliness also
dramatically affects a diamond's beauty.
The carat weight measures the mass of a diamond. One carat is defined as a fifth
of a gram, or exactly 200 milligrams. The point unit—equal to one one-hundredth
of a carat (0.01 carat, or 2 mg)—is commonly used for diamonds of less than one
The price per carat does not increase smoothly with increasing size. Instead,
there are sharp jumps around milestone carat weights, as demand is much higher
for diamonds weighing just more than a milestone than for those weighing just
less. As an example, a 0.95 carat diamond may have a significantly lower price
per carat than a comparable 1.05 carat diamond, because of differences in
||Cost per carat (US$)
||Total cost (US$)
|0.5 carat (50 points)
Total carat weight (t.c.w.) is a
phrase used to describe the total mass of diamonds or other gemstone in a piece
of jewelry, when more than one gemstone is used. Diamond solitaire earrings, for
example, are usually quoted in t.c.w. when placed for sale, indicating the mass
of the diamonds in both earrings and not each individual diamond. T.c.w. is also
widely used for diamond necklaces, bracelets and other similar jewelry pieces.
Clarity is a measure of internal defects of a diamond called inclusions.
Inclusions may be crystals of a
foreign material or another diamond crystal, or structural imperfections such as
tiny cracks that can appear whitish or cloudy. The number, size, color, relative
location, orientation, and visibility of inclusions can all affect the relative
clarity of a diamond.
Diamonds become increasingly rare when considering higher clarity gradings. Only
about 20 percent of all diamonds mined have a clarity rating high enough for the
diamond to be considered appropriate for use as a gemstone; the other 80 percent
are relegated to industrial use. Of that top 20 percent, a significant portion
contains one or more visible inclusions. Those that do not have a visible
inclusion are known as "eye-clean" and are preferred by most buyers, although
visible inclusions can sometimes be hidden under the setting in a piece of
Most inclusions present in gem-quality diamonds do not affect the diamonds'
performance or structural integrity. However, large clouds can affect a
diamond's ability to transmit and scatter light. Large cracks close to or
breaking the surface may reduce a diamond's resistance to fracture.
A chemically pure and structurally perfect diamond is perfectly transparent
with no hue, or color. However, in reality almost no gem-sized natural diamonds
are absolutely perfect. The color of a diamond may be affected by chemical
impurities and/or structural defects in the crystal lattice. Depending on the
hue and intensity of a diamond's coloration, a diamond's color can either
detract from or enhance its value. For example, most white diamonds are
discounted in price as more yellow hue is detectable, while intense pink or blue
diamonds (such as the Hope Diamond) can be dramatically more valuable.
Most diamonds used as gemstones are basically transparent with little tint, or
white diamonds. The most common impurity, nitrogen, replaces a small proportion
of carbon atoms in a diamond's structure and causes a yellowish to brownish
tint. This effect is present in almost all white diamonds; in only the rarest
diamonds is the coloration due to this effect undetectable. A rating system for
color in white diamonds grades them from "D" to "Z" (with D being "colorless"
and Z having a bright yellow coloration). Diamonds graded D-F are considered
"colorless", G-J are considered "near-colorless", K-M are "slightly colored".
N-Y usually appear light yellow or brown.
Diamond cutting is the art and science of creating a gem-quality diamond out of
mined rough. The cut of a diamond describes the manner in which a diamond has
been shaped and polished from its beginning form as a rough stone to its final
gem proportions. The cut of a diamond describes the quality of workmanship and
the angles to which a diamond is cut. Often diamond cut is confused with
There are mathematical guidelines for the angles and length ratios at which the
diamond is supposed to be cut in order to reflect the maximum amount of light.
Round brilliant diamonds, the most common, are guided by these specific
guidelines, though fancy cut stones are not able to be as accurately guided by
The techniques for cutting diamonds have been developed over hundreds of years,
with perhaps the greatest achievements made in 1919 by mathematician and gem
enthusiast Marcel Tolkowsky. He developed the round brilliant cut by calculating
the ideal shape to return and scatter light when a diamond is viewed from above.
The modern round brilliant has 57 facets (polished faces), counting 33 on the
crown (the top half), and 24 on the pavilion (the lower half). The girdle is the
thin middle part. The function of the crown is to diffuse light into various
colors and the pavilion's function to reflect light back through the top of the
New diamond cuts are now all the rage in the diamond industry as for example a
design invented in 2003 and called the Genesis cut. This cut differs in shape
from the more traditional cuts in its concave surfaces and angles and resembles
a 4-pointed star.
Quality of Cut
In addition to carrying the most importance to a diamond's quality as a
gemstone, the cut is
the most difficult to quantitatively judge. A number of factors, including
proportion, polish, symmetry, and the relative angles of various facets, are
determined by the quality of the cut and can affect the performance of a
diamond. A poorly cut diamond with facets cut only a few degrees out of
alignment can result in a poorly performing stone. For a round brilliant cut,
there is a balance between "brilliance" and "fire." When a diamond is cut for
too much "fire," it looks like a cubic zirconia, which gives off much more
"fire" than real diamond. A well-executed round brilliant cut should reflect
light upwards and make the diamond appear white when viewed from the top. An
inferior cut will produce a stone that appears dark at the center and in some
extreme cases the ring settings may show through the top of the diamond as
In the gem trade the term light performance is used to describe how well a
polished diamond will return light to the viewer. There are three light
properties which are described in relation to light performance; brilliance,
fire, and scintillation. Brilliance refers to the white light reflections from
the external and internal facet surfaces. Fire refers to the spectral colors
which are produced as a result of the diamond dispersing the white light.
Scintillation refers to the small flashes of light that are seen when the
diamond, light source or the viewer is moved. A diamond that is cut and polished
to produce a high level of these qualities is said to be high in light
About a third of all diamonds will glow under ultraviolet light, usually a blue
color which may be noticeable under a black light or strong sunlight. Some
diamonds with "very strong" fluorescence can have a "milky" or "oily" look to
them, but they are also very rare and are termed "overblues." Their study
concluded that with the exception of "overblues" and yellow fluorescent
diamonds, fluorescence had little effect on transparency and that the strong and
very strong blue fluorescent diamonds on average had better color appearance
than non-fluorescent stones. Since blue is a complementary color to yellow and
can appear to cancel it out, strong blue fluorescence had especially better
color appearance with lower color graded diamonds that have a slight yellowish
tint such as "I" color or "J" color but had little effect on the more colorless
"D" through "F" color grades.
Although it is not one of the four Cs, cleanliness affects a diamond's beauty as
much as any of the four Cs. A clean diamond is more brilliant and fiery than the
same diamond when it is "dirty". Dirt or grease on the top of a diamond reduces
its luster. Water, dirt, or grease on the bottom of a diamond interferes with
the diamond's brilliance and fire. Even a thin film absorbs some light that
could have been reflected to the person looking at the diamond. Coloured dye or
smudges can affect the perceived color of a diamond. Historically, some
jewelers' stones were misgraded because of smudges on the girdle, or dye on the
culet. Current practice is to clean a diamond thoroughly before grading its
Maintaining a clean diamond can sometimes be difficult as jewelry settings can
obstruct cleaning efforts and oils, grease, and other hydrophobic materials
adhere well to a diamond's surface. Many jewelers use steam cleaners. Some
jewelers provide their customers with ammonia-based cleaning kits; ultrasonic
cleaners are also popular.
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