The diamond has always had an incredible power over people. For its sake, men risked their lives, and women forgot about the reputation. This stone dazzled its brilliance and inspired people to both great exploits and dirty crimes. But what made it so great?
From a mineralogical point, a diamond is one of the crystalline varieties of carbon. The graphite rod of a simple pencil has the same composition as the most desired precious stone on earth. The diamond consists of approximately 99.95% carbon. The remaining 0.05% has various elements that affect the color and purity of the crystal.
Diamond formation and extraction
The beauty and strength of the diamond were valued for ages. But only toward the end of the 19th century it began to be studied by chemists, physicists, geologists and mineralogists. Scientists have established the parameters of mineral formation, as well as its “rising” to the earth’s surface. The obtained knowledge allowed an improvement in the methods of discovering new deposits.
Diamonds formed at a depth of about 250-300 km from one to three billion years ago. The primary deposits were formed in igneous rock. Within, stones rise to the surface by so-called kimberlite (Africa, Russia) and lamproite (Australia) pipes. During exploitation, open-pit and shaft methods are used. The former is represented in a giant shell crater with a diameter and depth that can reach over one kilometer. They are formed as a result of the blasting operation, followed by exporting the ore to a screening plant. There, diamonds are extracted from the broken ground. The development of open-cut mining becomes economically unprofitable at a depth of 500-600 meters. But in rare cases, the funnels can reach one and a half kilometers. Then they move on to an underground (shaft) survey.
Prior to the kimberlite pipes’ discovery, diamonds were found in placer (secondary) accumulations. They are located in river valleys (alluvial deposits), as well as at considerable depths of several hundred meters. There the ore is extracted with the dredge’s help.
According to some reports, up to 85% of the extracted stones still fall on the placer accumulation. And the yield sometimes amounts to several hundred carats per ton of processed rock. It is also worth mentioning some crystals formed as a result of a large meteorite’s fall. They differ in small sizes and are the subject of exclusive scientific interest.
After the discovery of deposits in South Africa at the end of the 19th century, diamonds became much more accessible. Already in the first half of the last century, there were so many of them that the international corporation De Beers began full-scale advertising. Thanks to this the tradition to give a diamond ring for engagement appeared.
Since 1998 the UN has imposed a ban on the purchase of diamonds from a number of West African countries, including Angola, Liberia and Sierra Leone. It became known as history as the “Kimberly Process.” The reason; “blood stones” mined in the territory of military operations. And the money from the sale was used to finance insurgent movements, weapons, slave trade and other illegal actions. But it was not so easy to apply the law in practice. “Conflict” diamonds were simply exported to neighboring states that did not fall under the sanctions and were implemented there. They were also exchanged for weapons and medicine.
About 4C and just that
In the middle of the last century, the Gemological Institute of America developed a system for evaluating diamonds. According to it a set of criteria such as color, clarity, cut and carat weight (together known as 4C) determine the quality of the diamond. It is believed that the higher each of the components the rarer, and accordingly, the more expensive the mineral. But is it really so? Let’s investigate.
As with colored stones, insignificant differences in the color of a diamond to the untrained eye can cause a noticeable difference in price. There are not so many exceptional colorless diamonds. Most of them have a yellowish or brownish hue, which makes such rocks less desirable. In the laboratories of the Gemological Institute of America (GIA), the most authoritative diamond evaluator in the world, the color of the minerals is determined under controlled conditions. They’re compared to masterstones — the stones of various shades estimated by a scale from D to Z — from extremely colorless to specimens with a distinctly yellow, gray or a brown tinge.
More than 50% of diamonds emit a light under ultraviolet radiation. It is almost imperceptible to the human eye under normal conditions and called fluorescence. This effect is the result of a change in the molecular structure of a diamond. In stones with D-F colors (the first three scale marks), fluorescence is undesirable. And the more noticeable, the higher the discount at the sale (up to 45% of the Rapaport price list).
At the same time, fluorescence can visually improve the characteristic of a stone with a cheaper shade and make it commercially more attractive. The fact is that most often it has a bluish shade in the ultraviolet, giving the stone a more desirable visual appearance. This effect, on the contrary, may increase the price of such minerals.
The degree of a diamond’s purity is determined by the size, shape, position and number of internal inclusions that are noticeable with a tenfold magnification. Almost all diamonds have defects. They make every stone unique and dissimilar to each other. It is the imperfections that help specialists to distinguish natural diamonds from counterfeits. They may also identify a separate mineral.
In the GIA grading system, internally flawless diamonds belong to the FL (flawless) group. They are considered to be the rarest and most expensive. On the other end of the scale there are stones with inclusions (I group, i.e. “included”). You can easily see them with the naked eye.
An important role in the evaluation of the mineral is played by the defects’ locations. On the side of the faceted stone they have less influence on its transparency than if positioned under the table. Hence an exemplar with inclusions in the central part can be from 10 to 30% cheaper.
The correct cut is extremely important for a diamond. It can “visually improve” the stone with mediocre characteristics and make it more beautiful. The correct proportions, symmetry and polishing increases its brilliance.
The perfectly cut diamond dazzles with its play and reflects the light by every facet. But as with other precious stones, the cutter often tries to reduce the loss of raw material. Thus the processed rock may look too dim and ugly. And also it may have “windows” in the pavilion, the light in which is not reflected, but disappears without a trace.
The best choice for a diamond
In the face of the common misconception, some customers look for stones with a larger diameter and less carat weight with the idea that such diamonds look more expensive. Visually, such a stone seems larger than it really is. But because of the “broken” symmetry it will come off worse. If we talk about liquidity, the range of choice should be narrowed to stones with a color from D to H; purity, from FL to VS2; and the quality of polishing and symmetry, no lower than “very good”. Such stones reveal the beauty of a cut diamond.
Diamond carat weight
The carat weight and price are also closely interrelated. The bigger the mineral the more expensive it is per carat. However, in search of a better diamond, it is always more appropriate to sacrifice its mass than any other characteristic. And also it is worth remembering that if we took two stones of the same weight, color, purity and shape, but the cutting, polishing and symmetry of the first one were excellent with a lack of fluorescence, while the second one were just good and emitted a very strong blue glow, the difference in their prices could be from 15% to 60%.
The Rapaport price list
Compared with colored gemstones, the prices for which are not regulated by any institutions, the value of a particular diamond can be estimated using the Rapaport Diamond Report. It is updated every week and publishes two types of prices. The first on the round cut stones. The second one, for fancy cuts.
With other things being equal, the diamonds of the classical round form in fifty-seven faces, calculated and improved by the mathematician Marcel Tolkovski in 1919, are always more expensive. From the point of view of ideal proportions that optimize the play of light, there are no competitors. Stones of fancy forms — any that differ from the round in fifty-seven faces — lose from 20 to 40% in price depending on the size. For these cuts, symmetry is extremely important. Otherwise passing light will be deflected incorrectly, creating ugly effects.
Special attention should be paid to any old cuts. The culet, a small additional facet at the base of the pavilion resembling a spike, is often sawn down in these stones. To remove a well-viewed “window” in the center of such diamonds is possible only with the help of a re-cut. Therefore they are available with a discount of 10-30%.
The standards of the Gemological Institute of America (GIA)
The Rapaport price list is based on the standards of assessment of the Gemological Institute of America (GIA). The rest of the laboratories certify the stones in accordance with the terminology of the GIA. But their reports often greatly embellish reality. Thus when the seller refers to the Rapaport price list, it is more desirable that he presents the GIA certificate.
The Gemological Institute of America is the only one organization in the world that receives many grants from the state. Practically all laboratories are commercial. And they suffer very much from competition with their own kind. In order to increase customer loyalty, such organizations often overstate the real characteristics of the stones being evaluated, and much often not for a one scale mark. Very frequently, when you buy a diamond with no GIA certificate, you cannot save money, but overpay greatly.
Diamond price drop and the “bridging weight”
When people say that prices for diamonds have come down, this is primarily indicative of an increase in the discount from the Rapoport price list for certain groups of stones. Also, you should always keep in mind the oversized stone. If we look at the table, the difference in price between stones of 2.00-2.99 carats and 3.00-3.99 carats is more than 40%. Therefore the cost of a diamond weighing 2.8 carats will be calculated at a lower rate than the one at 3.00 carats. Although the visual difference between them is almost unnoticeable. Therefore, stones that have a “bridging weight” (close to the next interval) can be up to 40% more expensive than the Rapaport rate.
The situation is the same for diamonds weighing from 6.00 to 9.99 carats. Until recently, the last gradation table was with diamonds weighing 5.00-5.99 carats. But then Rapoport added another one for stones from 10.00 to 10.99 carats. Consequently, if the diamond weight falls within the interval from 6.00 to 9.99 carats, its value is calculated at a rate of 5.00 to 5.99 carats plus a premium.
Small stones weighing up to 0.5 carats are usually sold either at the report’s price or with a discount of up to 15%. But the less ideal the mineral (because of a bad cut, fluorescence or black inclusions), the harder it is to sell (for example, in view of the outstanding size); and the more accommodating the seller. However, whatever one may say, there’s no such thing as a free lunch and a price reduction of more than 50% is usually offered by those whose stones are estimated to be less stringent than GIA standards. Therefore, in order to avoid overpayment, it is necessary to consider not discounts, but a concrete stone, resorting to the help of an experienced specialist.