Diamond Information
The four Cs
Cut
 Of all the four Cs, cut has the greatest effect on a diamond's beauty. In grading,
cut evaluates the cutters skill in the fashioning of the diamond.
Diamonds have a unique ability to manipulate light efficiently. This unique
ability can be released and maximized only by cutting and polishing the diamond
to an extremely high level of accuracy. This also requires that the cutters
be willing to put forth a great deal of time and effort, adhere to some very
strict geometric standards and, most important, be willing to sacrifice carat
weight for superior craftsmanship. The American Gem Society Cut Grading System
considers not only the proportions of a diamond, but also the craftsmanship
of its overall symmetry and polish. It is unique in that it uses the latest
in technology to analyze the cut’s impact on the diamond’s light
performance. The first of the four Cs
Color
A truly colorless diamond is extremely rare. Most diamonds possess varying
degrees of yellow or brown and small, subtle differences in color can make
a substantial difference in value. Although increasing shades of yellow can
reduce the value of a diamond this does not necessarily reduce its beauty.
If a diamond is well cut, the diamond's refraction and dispersion often will
disguise certain degrees of coloration. Unless a diamond is a fancy color (or
any color other than colorless to light yellow or brown), the American Gem
Society Color Grading System places it on a 0 to 10 scale, 0 being colorless.
To accurately and consistently grade color, an American Gem Society trained
grader will utilize special lighting to compare the diamond being graded to
a set of American Gem Society Master Color Comparison Diamonds, which have
met exacting standards of cut, color, clarity, and carat weight. The diamond
is viewed face down and reassessed face-up for the most accurate and consistent
grade. The second of the four Cs
Clarity
Clarity is the evaluation of a diamond's internal and external characteristics.
The fewer inclusions or blemishes, the more desirable the diamond. Inclusions
are internal, that is, inside the diamond. Two of the most common inclusions
are crystals and feathers. Crystals are merely minerals trapped inside the
diamond; feathers are breaks in the diamond. Blemishes are usually very small
and are only on the surface of diamonds. To locate these tiny characteristics,
an American Gem Society member jeweler will use a binocular microscope that
magnifies the diamond ten times. Then, evaluating the size, location, nature,
number, and color of all the inclusions and blemishes, a clarity grade from
0-10 is assigned. Zero represents a diamond that is free of any inclusion or
blemish when examined by a skilled grader under 10x magnification and proper
lighting. The third of the four Cs.
Carat Weight
 Comparing the value of stones by weight is like comparing the value of paintings
by size. A wall-sized canvas by an unskilled artist may be bigger than a miniature
by Rembrandt, but it will not be worth more. The standard used to measure diamond
weight is the carat. A carat equals 1/5 of a gram (or 1/142 of an ounce). Each
carat is further divided into points, each point representing 1/100th of a
carat. While weight may be the least important of the four Cs in determining
value, it may be the easiest of the four Cs to gauge accurately and is the
most objective. All that is required is a delicately balanced scale capable
of weighting extremely small weights. Yet, despite the ease of measurement
and the relative unimportance of diamond weight, there are some facts you should
understand about weight and price.
First, as diamonds increase in size, their cost tends to increase geometrically
rather than arithmetically. Thus, a one-carat diamond may cost more than twice
as much as a one-half carat stone of equal quality. Also, as previously stated,
weight does not always enhance the value of a diamond. In fact, when a stone
is improperly cut, added weight may serve only to reduce its brilliance. For
these reasons, you should consult with an American Gem Society titleholder
or individual regarding the question of carat weight, especially as it relates
to the quality of the diamond's cut. The fourth of the four Cs.
Diamond Facts
Eighty percent of the diamonds mined annually are used in industry; 4 times
that production is grown synthetically for industry - that's a total of over
500 million carats or 100 metric tons. Diamond is a fundamental industrial
material that affects our daily lives. Because diamond is the hardest substance,
it is used to cut, grind, and polish most hard substances. It fashions stones,
ceramics, metals, and concrete, as well as eyeglasses, gems, and computer chips.
Its growing specialty-uses include blades, some used in critical surgery; specialty
windows; and heat spreaders. And of course diamond phonograph needles reproduced
music for 50 years.
Diamond has three primary roles in industry: it is used as a cutting tool,
it is imbedded in another material and used as a tool or abrasive, and it is
turned to powder or paste for grinding and polishing. Diamond is selected for
such use where its hardness and resistance to abrasion - its long working life
and fast cutting action - outweigh its costs. Moreover, diamond's resistance
to wear enables it to cut reproducibly time after time, a requirement of automated
production. Diamond machining tools for turning, milling, and boring are preferred
where finely finished surfaces of high precision are needed. Diamond is used
for machining a wide variety of plastics, glasses, and metals, shaping products
such as the drums for copying machines, polygon mirrors in laser printers,
and aluminum-alloy pistons in automobile engines. However, diamond cannot be
used for machining alloys of iron. Under intense machining conditions the diamond
abrades very quickly against some materials, apparently because of a high-temperature
reaction between iron and carbon.
The device used by GE to synthesize diamond was termed a belt device because
tungsten carbide rams were driven into a cavity contained by a doubly-tapered
carbide cylinder, contained in turn by a steel jacket - termed a belt. Between
the rams is a cylinder of graphite - a furnace - containing the material to
be raised to high temperature and pressure. Around the furnace assembly and
between the anvils and belt is a compressible material to contain the pressure
and accept the deformation; it has traditionally been a natural clay called "pipestone
clay" for its alternative use in tobacco pipes. A hydraulic press, capable
of perhaps 50 tons, drives the rams into the belt cavity, amplifying the force
at the interior to high pressure. An electrical current is passed between the
rams and through the conductive graphite, which heats in response; the clay
acts as a thermal insulator as well as a container for pressure.
Because of their transparency, thermal conductivity, or surface properties,
diamonds are used in many research instruments as windows. An application of
exceptional value in mineral and material science is a small device that generates
extremely great pressures in the space between two diamonds - the diamond anvil
cell. These devices are used in experiments on the nature of planetary interiors
and dense matter, from mimicking Earth's core to producing solid hydrogen.
The mechanics of creating high pressure are simple, involving just an application
of force onto a small area, but extreme pressure will not be achieved without
a material of supreme hardness, incompressibility, and strength - such as diamond.
Most materials, steel for example, will deform or break before reaching pressures
that exist deep within Earth. Tungsten carbide is better, but diamond is best.
By polishing the ends off two fine round brilliant diamonds to a width of a
millimeter or so, and carefully and accurately squeezing them together, pressures
comparable to the center of Earth - 4,500,000 atmospheres - can be achieved.
At these pressures hydrogen transforms into a metal - a state that might exist
deep within Jupiter. Research on planetary interiors and dense matter has been
advanced greatly by the use of diamond anvil cells, using lasers, optics, and
x-rays to probe these small samples to reveal their mysteries.
Hardness is not the only superlative property of diamond that makes it important
in industry and technology--its extraordinary thermal conductivity, low-friction
surface, and optical transparency put diamond into cutting-edge applications.
Many new products, like compact electronic devices, windows for optical devices
in demanding environments, and "no-wear" bearings, such as in the
space shuttle, utilize diamond. For these applications, a synthetic form leads
the way. This is CVD, so-named for the growth technique chemical vapor deposition.
At present the major commercial application for CVD diamond is in thermal
management, where diamond heat-spreaders conduct byproduct heat away from a
device. The material can be grown with a thermal conductivity close to that
of the best natural and high-pressure synthetic diamonds used until now as
heat spreaders. Thousands of suitable heat spreaders can be cut from a single
wafer of CVD diamond, making for efficient use. A CVD diamond coating on an
object can be polished to yield an extremely smooth diamond surface, ideal
for high precision and low friction, such as is needed for precision bearings.
CVD diamond wafers with high optical transparency are excellent for viewing
a wide portion of the electromagnetic spectrum in environments with extreme
temperature, corrosiveness, or radiation.
Diamond was discovered to be carbon in 1796, and it took more than 150 years
from that time until a method of diamond synthesis was invented. The secret
was pursued by many scientists but not unlocked until the 1950s, when diamond
was synthesized almost simultaneously by Swedish and American researchers.
Pressures of over 55,000 atmospheres and 1400C, plus molten iron to facilitate
the change from graphite to diamond, were necessary. Now some 80 tons of synthetic
diamonds are produced annually by General Electric, De Beers, and many others
for industrial firms.
From the time Smithson Tennant showed that diamond was carbon, experimenters
tried to synthesize diamond from graphite or lamp black. Attempts over the
next 150 years were all fruitless, although the trend toward experiments at
high pressure and temperature were in the right direction. The invention of
tungsten carbide in the 1930s provided a material that could achieve the pressure
containment necessary for growing diamond. Experiments in the 1940s by Harvard
professor Percy Bridgman were unsuccessful, but finally in the early 1950s
two teams succeeded. The first was led by Baltazar von Platen, at the Allmanna
Svenska Elektriska Aktiebolaget (ASEA) Laboratory in Stockholm, Sweden, in
1953, but this initial success was not publicized or published. Thus, on February
15, 1955, the General Electric team of Francis Bundy, Tracy Hall, Herbert Strong,
and Robert Wentorf claimed credit for the first reproducible transformation
of graphite to diamond. GE went on to become the largest producer of synthetic
diamond; De Beers follows, with many other manufacturers also contributing
to the annual output of synthesized diamonds.
As methods for growing diamond, both at high pressure and by chemical vapor
deposition, improve, and as science finds ways to take advantage of diamond's
properties, the potential applications of diamond's superlative properties
appear boundless. From super electronics, to indomitable optical windows, to
unscratchable surfaces - maybe the next watch bezel - diamond is an obvious
choice.
Managing heat, particularly in electronics, with large layers of CVD diamond
is a rapidly expanding field. One of the most imaginative of these is the three-dimensional
multi-chip module, which holds out the promise of an extremely powerful supercomputer.
To gain speed, electronics need to be as compact as possible, concentrating
waste heat as well. By stacking sandwiches of electronics and CVD diamond,
a supercomputer could be made small and cool enough to function. Diamond windows
for infrared devices are under development and should find their way into the
tough environment of laser-guided smart bombs and more constructive uses in
industry as well. The use of diamonds as radiation detectors, light emitters
in electronic displays, and coatings to make surfaces indomitable or unwettable
are being researched now. Beyond their imprint as a tool, diamonds will be
showing up in more and more products in the future, probably in your home electronics,
appliances, and automobiles.
Diamond Buying
What's the occasion? A birthday celebration? An important anniversary? To
declare, "I love you!" Or to ask, "Will you be mine forever?" Whatever
the emotion, nothing commemorates the moment quite like a diamond. However,
the one emotion that has no place in the diamond-buying process is fear.
 First, Buyer Beware.
If you're like most people, you know little or nothing about diamonds. That's
why the American Gem Society came into existence over 70 years ago. Thanks
to these gemological pioneers, we now have precise standards for evaluating
diamonds, commonly known as the four Cs: Cut, Color, Clarity, and Carat Weight.
The American Gem Society Diamond Grading Standards evaluate three of the four
value factors — cut, color, and clarity — on its own 0–10
scale. The scales begin at 0 (zero), the highest grade, and go down to 10,
the lowest. The three factors are expressed separately along with the fourth
factor, the carat weight of the gemstone, for the final AGS Grade. This "science
of diamonds" helps take the fear out of buying a diamond.
Shopping Tips
Choosing a diamond is a very personal decision. While not everyone will share
the same opinion as to what constitutes beauty, most people want a diamond
that expresses their individual taste and personality.
What quality diamond should you look for? Some people want the largest diamond
they can afford; some are more concerned about the color and want a near-colorless
gemstone. Still others are more concerned about a diamond's clarity. And all
want a diamond that is cut to reveal the beauty of the gemstone.
jewelry links |
