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For centuries, cultures have regarded diamonds as beautiful, magical, mysterious, and powerful. These precious stones have been sought after, fought over, and worshiped. Diamonds are associated with wealth, achievement, status, and love. The meaning and rarity of diamonds brings about much to consider when making a purchase. The rough gemstones must first be mined and cut. Once cut, diamonds are appraised to determine their value. Some of them undergo treatments to augment their appearance. Diamonds progress through these processes to be transformed into beautiful valuable pieces of personal adornment.
Diamond is a crystallized form of carbon that grows deep in the earth, under immense pressure and heat. This form of carbon crystal is the hardest natural substance known to humans. Diamonds are brought to the surface by volcanic eruption. These types of eruptions are referred to as pipe mines because they resemble pipes in the ground with molten minerals moving through them. The pipe’s surface layer is a clay-like rock known as yellow ground for its color. Under the yellow ground is a layer of a mineral referred to as kimberlite. Both layers serve as matrices for diamonds. This mining process originated in India over 4,000 years ago, and the modern mining industry began with discoveries in South Africa in the late 19th century. Today, the top seven diamond producing countries, accounting for 80 percent of the world’s rough diamond supply, are Botswana, Russia, South Africa, Angola, Namibia, Australia and Zaire. (Levinson 234)
A good deal of technology is used in mining diamonds. The matrix is removed by blasting and by automatic block carving machines. The rock is first broken up into smaller pieces, then the waste is removed, and the concentrate with the gemstones is left behind. The extraction of the diamond from the concentrate was formerly done by hand. Extraction from the matrix is now done by putting the concentrate on a vibrating belt greased with fatty substances that are adhesive to diamonds. Further separation is done by optical selection with the use of photocells and x-ray technologies. On average one ton of diamond ore yields half a carat of diamond (one or more diamonds adding up to less than the volume of a pencil eraser). (Levinson 246)
Once the rough gemstones are extracted, they must be evaluated. The evaluation determines whether the diamonds are worth cutting for use in jewelry. Only about 20 percent of diamonds mined are used for adornment purposes. The rest of them are ground up and used for grinding wheels, glasscutters, milling cutters, and scientific purposes. The diamonds that are worth cutting are cut in a myriad of styles and shapes. The brilliant cut is the most common, as shown in figure one.
Fig. 1. Brilliant cut diamond and ideal proportions; rpt. in GIA.
There are several steps to cutting and polishing a diamond. The laps (cutting wheels) used in the process are all coated with diamond because the only material hard enough to cut diamond is another diamond. First, the rough diamond is cleaved. This means that the gemstone is sawn to prepare it for initial shaping. Once cleaved, the gem goes through the bruting process where it is given a shape with a girdle, crown, and pavilion. The final facets are then put on the gemstone and it is polished. The diamond is then ready for appraisal. (Levinson 238)
It is important to understand how the quality of a diamond is determined, and why some diamonds are more rare and valuable than others are. Value depends on quality, and the quality of a diamond depends on four characteristics called the 4Cs: Cut, Color, Clarity, and Carat weight. (GIA) What do these terms mean when it comes to buying a diamond, and is one “C” more important than another is? To make it simple, the larger the diamond, the rarer it is (carat weight); the purer the diamond, the more valuable it is (clarity); the less color in a diamond, the more beautiful; and the more precise the cut of the diamond, the more brilliant it is. The combination of these individual factors makes up the diamond’s overall quality and determines its beauty.
Once the diamonds are cut, they must be appraised to determine their characteristics and value. Cut and shape are often confused. Shape is only part of the cut. Shape is the form created by the stone when looking upon it from a top view. Common shapes for diamonds to be cut are round, pear, emerald, heart, oval, and marquise. These shapes are pictured in figure two. The shape of the diamond does not affect its value.
Fig. 2. Common shapes for cut diamonds; rpt. in GIA.
Most round diamonds are cut to have 58 facets. It is the work of a master cutter that allows a diamond to be cut in such a way as to permit the maximum amount of light to be reflected through a diamond. This creates a good brilliance or sparkle. (GIA)
There are several cuts of diamonds. The one with the greatest value is the ideal cut. The ideal cut diamond describes a round brilliant diamond that has been cut to exact mathematically derived proportions. Its symmetry produces great luster and beauty. When a diamond is cut to the ideal proportions all of the light entering from the top of the gemstone in any direction is reflected back through the top and is dispersed into a display of colors. The other cuts are deep and shallow cuts. In the deep cut light is lost through the sides of the diamond because the diamond is too deep, the result is a dark spot in the center. A shallow cut loses light through the bottom of the gemstone because it is too flat; the result is a gray ring inside the table edge. (GIA) These diamond cuts are illustrated in figure three.
Ideal Deep Shallow
Fig. 3. The different proportions of cut diamonds and their light refraction; rpt. in AGS.
The American Gem Society (AGS) was the first national organization to develop and use a system for determining how well a diamond is cut based against the ideal proportions. The cut grade system uses a scale ranging from zero, being ideal, to ten, being poor. (AGS)
Diamonds were formed under intense heat and pressure, and traces of other elements may have been incorporated into their atomic structure accounting for the variances in their color. (Schumann) Diamonds generally range from a shade of yellow or brown to colorless. There are diamonds of other colors such as pink, red, green, blue, orange, and black. These exceptions are rare and sometimes induced by treatments. Diamonds are graded by their color, the AGS and the Gemological Institute of America (GIA) developed color-grading scales. The scales and some sample stones are pictured in figure four. Colorless and fancy yellow diamonds are considered the most valuable. The differences in color grade are subtle, only a trained professional can properly determine the color grade. (GIA)
GIA – D E F
G H I J
K L M
N O P Q R
S T U V W X Y Z
AGS -0 .5 1.0
1.5 2.0 2.5 3.0
Near Colorless 3.5 4.0 4.5
Faint Yellow 5.0 5.5 6.0 6.5 7.0
Very Light Yellow 7.5 8.0 8.5 9.0 9.5 10
Fig. 4. The AGS and the GIA color grading scales with samples; rpt. in GIA.
Diamonds, more than any other gemstone, have the capability of producing the maximum amount of brilliancy. Clarity is an indication of a diamond’s purity. All diamonds, except the most rare, have tiny traces of minerals, gases, or other elements that were trapped inside during the crystallization process. These inclusions may look like tiny crystals, clouds, or feathers. A diamond that is free of interior inclusions and exterior blemishes (commonly called flaws) is of the highest quality. The absence of flaws in a diamond allows for no interference with light, creating a fiery gemstone. Less than one percent of all diamonds ever found have had no inclusions and can be called flawless or internally flawless. (GIA)
To determine a diamond’s clarity a professional with a trained eye uses a 10x-power binocular microscope. There are two systems for clarity grading developed by the AGS and the GIA; the GIA system is illustrated in figure five.
Fig. 5. The GIA clarity grading scale with samples and explanation; rpt. in GIA.
A carat is a unit of measurement used to describe the weight of diamonds.
One carat is divided into 100 points, so that a diamond of 75 points weighs .75
carats. There are five carats to one gram. Size is the most obvious factor in
determining the value of a diamond, but two diamonds of equal size can have
unequal values depending on their other qualities. Diamonds of high quality can
be found in all sizes, although there may be temporary shortages in certain sizes
and qualities due to supply, demand, and availability of rough. (Schumann)
Treatments and Synthetics
Diamonds are exposed to several treatments to enhance their quality. One treatment is laser drilling, commonly used in the clarity enhancement of diamonds. A focused laser beam is used to drill a narrow channel from the surface to dark inclusions, which may then be acid bleached. Another treatment is artificial irradiation, which has attained some importance due to the coloring effect produced when the stone is bombarded with particles of atomic size. Irradiation produces a green color, which can be further altered to fancy yellow, brown, orange, and rare pink by subsequent heating under controlled conditions. (EGL)
One of the most controversial gemstone treatments to appear in the last decade is the filling of surface reaching breaks in faceted diamonds. The filling of diamonds has proven to enhance diamond clarity by two grades. (Kammerling 145) The diamonds are first cleaned, then filled with a molten glass at high temperatures, cooled, and cleaned again to remove glass from the stones’ surfaces.
Claims have been made concerning the stability and durability of various products. It is virtually impossible to determine exactly how many treated stones are in the marketplace. Recent findings by gemologists indicated that the filling material used in at least one of the treatment processes might decompose when exposed to an ultraviolet lamp or ultrasonic cleaning. The GIA has learned that, while ultrasonic cleaning for a brief period may not damage at least some fillings, extended exposure to this process may cause some shattering of, or other damage to, the filler. High temperature torches used in various jewelry repair procedures may also have adverse affects on treated gemstones. Because of industry concerns about disclosure and detection, it has been suggested that all such stones be laser-inscribed with initials to disclose the treatment. (EGL)
Synthetic diamonds are also on the market. Some of the synthetics have the same exact properties as natural diamond. In 1990, scientists at the General Electric Research and Development Center (GERDC) in New York, announced the production of a new isotopically pure carbon-12 synthetic diamond. Carbon, in nature, consists of a mixture of carbon atoms that have different masses called isotopes. Natural diamond has carbon atom isotopes twelve and thirteen, as do the GERDC synthetics. (EGL)
Two additional C’s should be mentioned. One of the most important for the consumer is the “C” in cost. The most obvious of the 4C’s is the carat weight or the size of the stone, which is one of the bigger factors in determining value of a diamond. The combination of all four characteristics is the final determining cost factor. There are many different combinations of size, color, clarity and proportioning that will affect the final value. (DiNola)
Finally, there is the last “C” confidence, confidence in your jeweler. When you are ready to choose your diamond, see a reliable jeweler, one who is trained and will be happy to explain the four C’s to you. He or she will tell you the difference between various qualities of diamonds and how these differences affect the price. Do not expect to find any “bargains” in diamonds, quality has its price. An established jeweler prizes his good reputation and will help you choose the best quality diamond. He or she knows you are looking for quality when you are making one of your most important purchases. (DiNola)
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