27 Jan 12 Precious Colored Diamonds
A diamond is the world’s exceptionally precious gemstone, but the beauty of colored diamonds is something which every gemstone might crave for. Being the most admirable and rare, colored diamonds are the dream of every investor, collector and connoisseur. It is the most sought after gemstone and an investment of a lifetime. An interesting fact about a colored diamond is that it is the most rarest among 10,000 carats of diamonds. In simple words, only 1 carat are colored out of 10,000 carats.
These fancy diamonds are available in vibrant red, blue, green, purple, yellow and so many other hues. Important factors to be considered while grading colored diamonds are their fancy & vividness, which depends on their color and saturation. The beautiful colors of these diamonds are a result of presence of trace elements within the carbon crystal structure of a diamond.
Common colors found are mentioned below
Yellow : When nitrogen is present as an impurity in the crystal structure of diamond, it appears as yellow color.
Blue and grey : The presence of boron (hydrogen) results in formation of this color.
Green : Green color is due to the ‘vacancy color center’ phenomenon.
Gemology defines it as the vacancy in the atomic structure of carbon.
Pink, mauve,brown : These colors are created by plastic distortion.
In other words, due to disfigurement of the internal frame of the diamond.
The rarity of the colored diamonds is marked by the fact of their 1 percent presence amongst the world’s total diamond. Hence, they can be aptly addressed as priceless. Red is the most rare color found in diamonds and because of rarity, diamonds undergo HPHT treatment- or the High Pressure High Temperature treatment to form color. In this treatment, diamonds are put under high pressure and high temperature to transform the crystal structure and create brown diamonds colorless and diamonds with nitrogen into a deep yellow-green color.
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14 Oct 11 Diamond the Premier Mineral
Diamond is a stable allotrope of carbon. Allotropy is chemically the ability of an element to exist in more than one form in the same physical state. The second allotrope of the same element is graphite. The characteristic different in the two allotropes is in their chemical bonding, where both are covalently bonded but their atomic combinations is different. In diamond, every single carbon atom is covalently bonded to 4 other carbon atoms, hence utilizing all delocalized electrons in carbon. Commercial properties of diamond including poor electrical conductivity are as a result of this chemical composition.
Chemical facts – physical properties of diamond
Physically, diamond is a shiny solid, crystalline in nature. It’s colorless and transparent. One of the best known qualities of diamond is its hardness. Mineral experts have argued that it is the hardest mineral in existence. The hardness of diamond is attributed to its intrinsic chemical composition (Thomas, 1991). Chemically, carbon, with an electronic configuration of 2, 4 require 4 electrons in its outermost energy level to attain stability. In diamond, this is achieved through covalent bonding where each atom combines covalently with 4 others. This implies that the 4 outermost electrons are effectively used up in bonding. The resulting structure from this combination is an octahedral structure that extends in all directions. The covalent bonds are very strong making it very hard to break it. The melting point is considerably high, estimated at 37000c.
Another common property is its poor electrical conductivity. This comes as a result of lack of delocalized electrons in its bonded structure. Recent developments have seen diamond being used as an insulator where it’s first doped with boron, an element that creates gaps within the octahedral structure making it possible to conduct. The Boron impurity also makes the diamond appear blue in color. The physical appearance of diamond is primarily clear colorless (Thomas, 1991). This is because it has a band gap of approximately 5.5eV. This band gap chemically corresponds to an ultraviolet radiation wavelength of approximately 225 nm. Other colors associated with diamond, principally originates from impurities and lattice defects. Using technology the impurities are introduced in diamond in a process referred to as chemical growth in diamond. The dominant impurity in diamond is Nitrogen which makes the diamond appear yellow or brown. Boron impurities make the diamond appear gray bluish. Other colors such as red and green are achieved through plastic deformation which involves the physical deformation/ disorganization of the diamond crystal.
Identification of Diamond
The principal identification method is based on the hardness and their high thermal conductivity (Boser, 2008). The material also has a high thermal conductivity, though this cannot be relied upon because other materials also exhibit a similar r property. In the Mohs scale, diamond follows quartz on the ability to cut glass so the ability to cut glass is not a conclusive test. Another test is the ability of diamond to scratch other diamonds though this normally results in the destruction of both pieces (Thomas, 1991). In the laboratory, special techniques such as spectroscopy, luminescence and microscopy are normally applied. In luminescence, the diamond is normally illuminated using shortwave ultraviolet radiations. Special machines are also used in identification. Diamond sure and Diamond view are specially made machines developed to test the authenticity of marketed diamond.
Natural Formation of Diamond
Naturally, diamond is crystallized from fluids containing high carbon content. This crystallization, achieved industrially is achieved using considerable amounts of heat and pressure. Heat needed is approximately 20000 F and 50000 pa of pressure. These kinds of pressure and temperatures are only found occurring at surfaces deep below the sea level. It is the belief of most scientists that diamonds form in depths well below 150 km below the earth’s surface (Hesse, 2007). The quantities of diamond enough to satisfy the industrial and commercial purposes are found in some geologically rich places scattered in some parts of the Earth’s continent. Most continents are formed of cratons which consists are the primary content of the earth’s crust formed approximately more than 2 billion years ago. Scientific dating has established that some diamonds could have formed more than 3 billion years ago. The current deposits of diamond are estimated to originate from volcanic rocks which are believed to have been deposited in strategic places through massive volcanic activities (Hesse, 2007). Deposit of diamonds available today is results of alluvial deposits which have resulted through weathering and movement by water. Strong winds and glacial movement have in the past contributed to transportation of diamond across different geographical positions in the Earth. Tectonic movements have also been credited with moving diamond deposits from great depths. Such kinds of deposits have been found in laces such as Kazakhstan. Diamonds found in this manner are generally of poor quality due to the intensive processes it has gone through which it is passed (Thomas, 1991). Meteorites have also been credited to formation of small deposits of diamond. The quality of these diamonds is generally of lower density. Some diamonds are estimated to form from extra terrestrial formations. There is possibility that most of the diamond in Africa and some parts of North America were formed in such processes.
Cutting of Diamond
For industrial and synthetic uses, diamond is passed through several processes. Natural diamond is normally rough. Due to its hardness, a lot of heat energy is needed to enable cutting. The cutting process includes laser cutting, sawing, cleaving and the final process of polishing. When cutting, the intention is to enhance the quality of diamond without losing a lot of quantity. About half of diamonds quantity is normally lost during cutting. The first step involves examination of the stone t determine the points of crystal weakness(Thomas, 1991). The cutter determines the planes that can easily be cut via sawing and cleavage. Present day cutters normally utilize the laser beam in achieving cleavage rather than traditional cleavage. The final process involves polishing the cut stone. The stone is considered polished when all of the facets are polished.
Judgment of Quality
When a diamond is used for jewellery, the properties that buyers should consider are clarity, color, carat weight and cut (Boser, 2008). Diamonds containing tainted colors of brown and yellow are considered of low value while special colored stones with tinges of green and orange, blue and red are considerably rare and hence of high value. Clarity is determined by presence of blemishes or not. Absence of blemishes ensures that the diamond cut is of great clarity. The carat weight is an attribute to the size of the diamond. The metric carat normally used for measuring diamond is approximately 0.2g. The cut quality reflects the quality of the processes of cleavage and polishing.
Uses of Diamond
Almost 80% of diamond normally contains impurities which lowers its color quality required in jewellery making. Most of it is used for manufacturing purposes. Since it is extremely hard, the metal is used in making hardy drill bits for cutting devices and in making surfaces that can withstand extreme shock (Thomas, 1991). Scientifically, it is used in photo detection and radiation and in experiments involving high pressures and temperatures.
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26 Sep 11 Color Grading of Diamonds
Most people don’t know this, but diamonds come in every color of the rainbow. Diamonds are made of carbon. When nature adds different elements to the carbon it creates different colors. Adding boron will give the diamond a blue color, nitrogen makes them yellow, hydrogen gives violet hues and so on. Most consumers are looking for the traditional colorless or near colorless diamond that is used in bridal and fashion jewelery in retail stores.
Diamonds are graded on a color chart that is recognized around the world. The chart starts with the letter D (think D for Diamond) and runs all the way to Z.
D, E, F, G, H, I, J, K … Z
Starting with the letter D and going to F are what are called colorless diamonds. These diamonds have an absence of yellow in them and are more rare to find in nature. They offer a beautiful white appearance but of course cost more because of the rarity of them.
Diamonds graded G-J are called near colorless.
These diamonds will have start to have a very slight tint of yellow and are more common in the marketplace. Typically all fashion pieces like necklaces, earring, bracelets, etc. are going to be in this quality. One of the reasons why is because a fashion piece tends to have many diamonds on it and if they were all colorless it would make the price spike fairly quickly. Near colorless diamonds offer affordability and allow the jewelry to have a higher total carat weight.
Anything running from K-Z is going to have a visible yellow color. The closer you get to Z the more yellow a diamond will have. It is around the Z range that you will start to see what some refer to as Canary diamonds. Just as a D color is rare, a Z is the same way.
The price for a diamond that starts to get close to Z with an intense or vivid yellow color starts to increase because of it’s rarity.
A jeweler trying to determine the coloring of a diamond will have a set of what are called master stones. These stones are made of a synthetic stone called cubic zirconia (CZ). These CZ’s are shaded from D-Z just as if they were real diamonds. The jeweler will hold a real diamond next to these master stones to determine the coloring of it. To tell the difference between a G and an H diamond is very difficult, even for a seasoned jeweler. Having these master stones is a great visual reference point for getting a more exact idea of what color the diamond is that is being looked at.
As stated before, most fashion jewelery is near colorless which is standard. But when you start shopping for an engagement ring, you’ll need to pay closer attention to the color of the diamond you’re thinking of purchasing. This is going to be the center stone of her engagement ring that she’ll look at forever and you sure don’t want it to be a dull or murky yellow. Here are a few pointers:
If you’re going to be putting the diamond into what’s called a solitaire (a thin band of gold or platinum with just the one diamond on it, no side diamonds) you need get a diamond in a color that’s going to be complimentary to the metal of the band. If you’re getting a white gold or platinum solitaire you need to get an H color or better. Anything I or below will have a yellow tint that will contrast with the white color of the metal and will make the yellow in the diamond very visible. If you’re going with yellow gold you can usually get away with anything because the yellow in the metal will blend with the yellow in the diamond. Keep in mind though that if you purchase a colorless diamond, even a D, and you put it into a yellow gold band, you might see some of the reflection of the yellow metal bounce up into the colorless diamond. It’s a very very faint reflection but if you think this might bother you, save the money and go for a G-H, they will blend and hide the reflection.
If you’re purchasing a ring that’s going to have side diamonds, you need to get a center stone that is comparable in color to the sides. There’s no need in buying a D if the side stones are an I. The beautiful whiteness of the D will make the side diamonds look dirty.
I worked in the jewelery industry for 7 years and have sold engagement rings from a couple hundred dollars to over fifteen thousand dollars. Here is my opinion:
Go for a G color. The reason is because it looks just as white as a colorless diamond without having to pay the price for one. Most people who purchase a colorless are doing so because it’s at the top of the chart and “high quality”. Almost 95% of the time that I would hold 2 diamonds next to each other, one an F and one G, and asked the customer to tell me which was which, no one could ever tell the difference. Typically you have to have a 2 color grade difference to see a change in color. That’s why jewelers use master stones, it’s hard to tell a G from an H or even more so from an E to an F. As an average consumer (even myself most times) you’ll usually have to strain to see the visible difference between an F and G but not the difference in the jump in price . The reason is because you’re jumping from the near colorless category to colorless. No real visible change, but a category change. Save your money and buy a G. It’s not like you’ll be walking around all day with 2 diamonds comparing them. A G is affordable, offers a wonderful color (or lack thereof) and will work with any ring you put it into, whether it’s a solitaire in yellow or white gold or it has side diamonds.
20 Jun 11 Hpht Diamonds
History of HPHT
The history of HPHT treatments dates back to 1955, when the General Electrical Company 1st discovered the process for creating diamonds within the laboratory. This led to the creation of HPHT process, whereby GE initial created a press where the required pressure and temperature might be maintained for the process. One factor led to a different and HPHT treatment evolved through numerous presses like the tetrahedral, BARS and finally the cubic press. What began as an experiment for diamond color modification in artificial diamonds has today evolved into usage for natural diamonds also.
Usage of HPHT Diamond Enhancements HPHT treatments primarily serve 2 functions
?Creation of artificial diamonds
?Color modification in natural diamonds
Creating artificial diamonds: To obtain artificial diamonds, carbon is put within a grapite capsule. A seed is then inserted into this capsule and a catalyst is added. The diamond grows on the seed whereas the catalyst allows the crystallization to require place.
Color modification: Completely different sort of diamonds react differently when exposed to HPHT treatments and a vary of colors are obtained. For instance, diamonds containing aggragated nitrogen, when exposed to HPHT will cause it to become single substitution nitrogen. In such cases, diamonds having green, orange and yellow hues will be created. In diamonds where nitrogen is negligible, the method is typically used to supply colorless diamonds. Therefore brownish diamonds when HPHT processed can obtain a colorless hue. A light pink color could additionally be obtained in some cases. In case of diamonds with negligible nitrogen and presence of boron, HPHT will alter the color. Therefore brownish diamonds will lose the brown tone and boron can make the stone bluish in color.
Popular presses used for treatment
Belt presses: This was the initial type of press used for treatment. Here pressure is formed by the usage of 2 high strength pistons that provide equal pressure in opposing directions on a sample. A series of rings surround the sample in order to contain the pressure.
Torid press: During this method, the 2 pistons apply pressure in an exceedingly single vertical direction.
Cubic press: This uses many pistons that provide pressure from completely different directions. It’s also known as a tetrahedral press.
Procedure of HPHT
If a client intends to convey diamonds for this treatment, the subsequent procedure is used,
?The stone is 1st inspected by diamond experts for cracks, fractures etc. Stones also are subject to chemical analysis using scientific equipment. Once it is confirmed that the treatment can be undertaken, the same is informed to the customer.
?Relying upon the properties of the stone, the color that may be obtained when treatment is deciphered and the customer is informed concerning the same.
?Pressure of over 1,000,000psi is applied by placing the stone in an inside pressure medium that distributes the pressure on the complete diamond equally.
?The internal pressure medium is placed into a heat generating sleeve where temperatures start at 1800 degrees centigrade.
Pricing of treatments: Price for these treatments varies with the scale of the diamond. Additionally the overall number of stones given and additional services like repolishing are charged extra. Whereas these treatments are expensive,
Organizations and HPHT
Because HPHT is controversial, totally different bodies follow different pointers for HPHT. As per the Federal Trade commission, HPHT treated diamonds should be disclosed to the user. General Electrical follows this norm and all diamonds that are HPHT treated are laser inscribed with the terms ‘HPHT PROCESSED’, IRRADIATED. If GIA notes diamonds to be HPHT treated, it additionally specifies them as ‘HPHT ANNEALED’ or ‘Artificially Irradiated’. Such details are displayed prominently on the grading report below ‘origin’ within the ‘color’ section of the report.
Execs and cons
The HPHT treatment of diamonds is a controversial issue as a result of it has each blessings and disadvantages. These are more discussed as under.
Benefits
?The treatment is permanent and diamonds are stable in the conventional conditions of wear and care.
?It can dramatically alter the colour of brownish diamonds to create it more appealing. Light-weight brown color diamonds will be rendered virtually colorless using this process.
Disadvantages
?The method causes surface graphitization and therefore the diamond desires to be polished to get rid of it.
?It is tough to differentiate between regular natural diamonds and HPHT treated diamonds.
?It will cause marginal weight loss during a diamond.
?It can scale back the clarity of the stone.
Disclosure
As HPHT has become a lot of commercially on the market, today there are various ways on the market to detect if your stone has been HPHT processed or not. At the fundamental level diamonds over 0.five carat will solely be HPHT treated. A trained gemologist may use equipment like the SSEF spotter and crossed polarization filter to detect the same. DiamondSure is additionally used to separate cape diamonds from the rest. At the following level FTIR and UVVIS spectroscopes are used and synthetic and PT treated diamonds will easily be identified ere. Besides this, renowned laboratories have several alternative proprietary procedures that they use to spot such diamonds.
With all refined equipment it continues to be difficult to detect HPHT processed diamonds at many instances. It’s so necessary that you purchase diamonds from a trusted vendor on-line or offline. Diamonds accompanied with a certificate from a reputed laboratory like GIA conjointly guarantee that diamonds are completely natural. You’ll additionally select signature or prime of the road branded diamonds to shield yourself. Finally, if you cannot afford GIA stones, create positive to choose a diamond that’s in the course of a certificate from a renowned laboratory.
