Such a practice is not there anywhere in the world — including Antwerp and Tel Aviv. Besides that, even in the Kimberley Process manuals, there has never been any attempt to describe roughs — the way the customs department mandates, they say. These are packed in smaller packets and after some preliminary mine-level assortment, these are sent to polishing hubs like India.
That apart, miners such as Alrosa, Dominion, Rio Tinto and DeBeers have their own set of classifications for the roughs. According to industry body officials, miners who do auctions of rough diamonds do not reveal the exact grading and classification of roughs. They do not do so because those specs may help diamond traders estimate the price of the packet. This may not bode well for the miners during auctions. Diamond Producers Association DPA , the body representing seven leading mining companies of the world, has also come in support of the diamond traders.
Many diamond traders view the new custom declaration rules as a fall-out of the Nirav Modi-Mehul Choksi scam. But they should not trouble good businessman. The impasse between diamond traders and customs department is not likely to end anytime soon. Read more on diamond cutting india. Punjab National Bank.
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Become a member. MensXP Mud launched with a community-driven approach. Mail This Article. My Saved Articles Sign in Sign up. Find this comment offensive? Type I diamonds have nitrogen atoms as the main impurity, commonly at a concentration of 0. If the nitrogen atoms are in pairs they do not affect the diamond's color; these are Type IaA.
If the nitrogen atoms are in large even-numbered aggregates they impart a yellow to brown tint Type IaB. Synthetic diamond containing nitrogen is Type Ib. They also have a characteristic fluorescence and visible absorption spectrum see Optical properties of diamond.
Type II diamonds have no measurable nitrogen impurities. They also have differing fluorescence characteristics, but no discernible visible absorption spectrum. Type IIa diamond can be colored pink , red , or brown due to structural anomalies  arising through plastic deformation during crystal growth—these diamonds are rare 1. Type IIb diamonds, which account for 0. However, a blue-grey color may also occur in Type Ia diamonds and be unrelated to boron.
Diamond color - Wikipedia
Pink and red are caused by plastic deformation of the crystal lattice from temperature and pressure. Opaque or opalescent white diamonds are also caused by microscopic inclusions. The majority of diamonds that are mined are in a range of pale yellow or brown color that is termed the normal color range. Diamonds that are of intense yellow or brown, or any other color are called fancy color diamonds.
Diamonds that are of the very highest purity are totally colorless, and appear a bright white. The degree to which diamonds exhibit body color is one of the four value factors by which diamonds are assessed. Diamonds have a color grading system that refers to the absence of color. This system goes from D to Z. The more colorless a diamond is, the rarer and more valuable it is because it appears white and brighter to the eye.
Color grading of diamonds was performed as a step of sorting rough diamonds for sale by the London Diamond Syndicate. As the diamond trade developed, early diamond grades were introduced by various parties in the diamond trade. Without any co-operative development these early grading systems lacked standard nomenclature, and consistency. Numerous terms developed to describe diamonds of particular colors: golconda , river , jagers , cape , blue white , fine white , gem blue , brown , etc.
The scale ranges from D which is totally colorless to Z which is a pale yellow or brown color. Brown diamonds darker than K color are usually described using their letter grade, and a descriptive phrase, for example M Faint Brown. Diamonds with more depth of color than Z color fall into the fancy color diamond range. Diamond color is graded by comparing a sample stone to a master stone set of diamonds.
Each master stone is known to exhibit the very least amount of body color that a diamond in that color grade may exhibit. A trained diamond grader compares a diamond of unknown grade against the series of master stones , assessing where in the range of color the diamond resides. This process occurs in a lighting box, fitted with daylight equivalent lamps.
When color grading is done in the mounting, the grade is expressed as an estimated color grade and commonly as a range of color. Grading mounted diamonds involves holding the mounted diamonds table close to the table facet of the master stone and visually comparing the diamond color under the same color conditions as unmounted diamond grading. The resulting grade is typically less accurate, and is therefore expressed as a range of color. While a grading laboratory will possess a complete set of master stones representing every color grade, the independent grader working in a retail environment works with a smaller subset of master stones that covers only the typical grade range of color they expect to encounter while grading.
A common subset of master stones would consist of five diamonds in two grade increments, such as an E , G , I , K , and M. The intermediate grades are assessed by the graders judgement.
If a diamond is located near radioactive mineral grains during its time within the Earth, it can be exposed to a stream of high-velocity particles. These high-velocity particles can knock carbon atoms out of their lattice position within the diamond.
Transforming Rough Diamonds
This vacancy defect can cause the selective absorption of red light and the selective transmission of green. When the transmitted green light reaches the observer's eye, the diamond will appear green. This is the cause of color in many naturally green diamonds. Pink Graining in Diamond: In this photomicrograph, you are looking into the interior of a rough diamond through a small polished window on its surface. The pink vertical lines are "graining" caused by plastic deformation of the diamond crystal lattice.
Diamonds in the Rough (The Diamond Collection Book 1)
Each line traces a slip plane within the diamond where carbon atoms have been displaced. In this view the slip planes intersect the polished window at a right angle. Each slip plane is a defect in the diamond that causes the diamond to selectively absorb green light and selectively transmit red. Note the tiny offsets where the slip planes intersect the edges of the polished window.
A small amount of pink graining in a diamond crystal can cause that diamond crystal to have a pink color. Where the amount of graining is very high the diamond crystal can have a red color. Pink and red diamonds are caused by the same type of defect. The color pink or red is determined by the abundance of pink graining in the stone. During their formation and residence within the Earth, all diamonds are exposed to the compressional forces of the deep Earth. In some diamonds, this stress can be applied in a manner that deforms the diamond's crystal lattice by displacing carbon atoms from their normal positions.
The deformation produces bands of slightly displaced atoms through the diamond crystal, known as graining. Graining can produce brown color in diamond , and in very rare instances, pink or red color. Sometimes, during microscopic examination, bands of dislocated atoms can appear as parallel color zones within the diamond. These features are known as "graining" because of their similar appearance to wood grain.
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