67834
Weight: 37.5 DWT ( 58.32 grams) Comes Set With Quantity Stone:
4 0.013 Ct -- 1.4-1.45 MM, GH-SI1 Round Diamond Round
34 0.017 Ct -- 1.5-1.55 MM, GH-SI1 Round Diamond Round
266 0.022 Ct -- 1.6-1.7 MM, GH-SI1 Round Diamond Round
360 0.026 Ct -- 1.7-1.8 MM, GH-SI1 Round Diamond Round
67834 / 18K White / 15 1/4 CT TW / Polished / DIAMOND BANGLE BRACELET
Item #: 67834:100:P
$27,347.26

67338 / 14K White / 3/4 CT TW / Polished / DIAMOND BANGLE BRACELET
Item #: 67338:102:P
Comes Set With
Quantity Stone
27 0.028 Ct -- 1.9 MM, I1 Round Diamond
$2,298.20 each


67336 / 14K White / 2 1/4 CT TW / Polished / DIAMOND BANGLE BRACELET
Comes Set With
Quantity Stone
120 0.019 Ct -- 1.7 MM, I1 Round Diamond
$3,174.84 each

68336 / 14K White/Yellow / 1 CT TW / Polished / TWO TONE DIAMOND BANGLE BRACELET
Comes Set With
Quantity Stone
42 0.006 Ct -- 1.1 MM, I1 Round Diamond
93 0.008 Ct -- 1.2 MM, I1 Round Diamond
$5,047.87

67504 / 18K White / 12CTTW SI1,GH 7 1/4" / Polished / DIAMOND TENNIS BRACELET
Comes Set With
Quantity Stone
36 04.30 MM (04.04 - 04.45) Full Cut, SI1 ROUND FULL CUT G-H GENUINE DIAMOND
$43,689.85
 

67416 / 18K White / 9CTTW SI1,GH 7 1/4" / Polished / DIAMOND TENNIS BRACELET
Comes Set With
Quantity Stone
39 04.10 MM (03.90 - 04.20) Full Cut, SI1 ROUND FULL CUT G-H GENUINE DIAMOND
$30,597.75

67046 / 18K White / 8 7/8 CT TW / Polished / DIAMOND BRACELET
Comes Set With
Quantity Stone
59 03.00 MM (2.88 - 3.18) Princess, SI1 SQUARE PRINCESS G-H GENUINE DIAMOND
$23,375.69

Enhanced New Fancy Color DIAMONDS: IRRADIATED AND/OR HPHT / SI ROUND FULL CUT GENUINE DIAMONDS now available in these colours:

TEAL BLUE
YELLOW
AQUA BLUE
DARK GREEN
APPLE GREEN
BURNT ORANGE
GARNET RED
BLACK STANDARD

PURPLE

ESCOMPTES en MAGASIN:

 Shape MM Size Size Ct Color Quality Cut Unique Attribute Availability Wgt Price/Ct Est. Price
Square 1.00 CT (.90 - 1.17) YELLOW SI Princess IRRADIATED AND/OR HPHT In Stock 1.0500 $8,342.50 $8,759.63
Square 1.00 CT (.90 - 1.17) TEAL BLUE SI Princess IRRADIATED AND/OR HPHT In Stock 1.0500 $8,342.50 $8,759.63
Round 1.00 CT (.90 - 1.17) TEAL BLUE SI Full Cut IRRADIATED AND/OR HPHT In Stock 1.0500 $6,932.50 $7,279.13
Round 1.00 CT (.90 - 1.17) YELLOW SI Full Cut IRRADIATED AND/OR HPHT In Stock 1.0500 $6,932.50 $7,279.13
Square .75 CT (.70 - .89) YELLOW SI Princess IRRADIATED AND/OR HPHT In Stock 0.7500 $4,817.50 $3,613.13
Square .75 CT (.70 - .89) TEAL BLUE SI Princess IRRADIATED AND/OR HPHT In Stock 0.7500 $4,817.50 $3,613.13
Round .75 CT (.70 - .89) 3/4 YELLOW SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.7500 $4,488.50 $3,366.38
Round .75 CT (.70 - .89) 3/4 TEAL BLUE SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.7500 $4,488.50 $3,366.38
Round .50 CT (.45 - .69) 1/2 TEAL BLUE SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.5500 $3,854.00 $2,119.70
Round .50 CT (.45 - .69) 1/2 YELLOW SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.5500 $3,854.00 $2,119.70
Square .50 CT (.45 - .69) YELLOW SI Princess IRRADIATED AND/OR HPHT In Stock 0.5500 $3,854.00 $2,119.70
Square .50 CT (.45 - .69) TEAL BLUE SI Princess IRRADIATED AND/OR HPHT In Stock 0.5500 $3,854.00 $2,119.70
Round 03.80 MM (03.55 - 04.00) .20 CT (.18 - .22) 1/5 PINK SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.2000 $8,131.00 $1,626.20
Round .37 CT (.37 - .44) 3/8 YELLOW SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.4100 $3,090.25 $1,267.00
Round .37 CT (.37 - .44) 3/8 TEAL BLUE SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.4100 $3,090.25 $1,267.00

Shape MM Size Size Ct Color Quality Cut Unique Attribute Availability Wgt Price/Ct Est. Price
Square 04.00 MM (3.88 - 4.20) .37 CT (.37 - .44) YELLOW SI Princess IRRADIATED AND/OR HPHT In Stock 0.3750 $2,890.50 $1,083.94
Square 04.00 MM (3.88 - 4.20) .37 CT (.37 - .44) TEAL BLUE SI Princess IRRADIATED AND/OR HPHT In Stock 0.3750 $2,890.50 $1,083.94
ROUND - BLACK 05.80 - 06.80 MM 1.00 CT (.9490 - 1.170) 1 BLACK STANDARD Full Cut COLOR ENHANCED In Stock 1.0500 $963.50 $1,011.68
Round 03.40 MM (03.24 - 03.54) .15 CT (.135 - .174) 1/6 PINK SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.1500 $6,744.50 $1,011.68
Round 04.30 MM (04.04 - 04.45) .33 CT (.29 - .36) 1/3 YELLOW SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.3300 $2,714.25 $895.70
Round 04.30 MM (04.04 - 04.45) .33 CT (.29 - .36) 1/3 TEAL BLUE SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.3300 $2,714.25 $895.70
Square 03.75 MM (3.68 - 3.87) YELLOW SI Princess IRRADIATED AND/OR HPHT In Stock 0.3100 $2,737.75 $848.70
Square 03.75 MM (3.68 - 3.87) TEAL BLUE SI Princess IRRADIATED AND/OR HPHT In Stock 0.3100 $2,737.75 $848.70
Round 03.80 MM (03.55 - 04.00) .20 CT (.18 - .22) 1/5 AQUA BLUE SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.2000 $3,619.00 $723.80
Round 03.20 MM (03.11 - 03.23) .12 CT (.115 - .134) 1/8 PINK SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.1200 $5,710.50 $685.26
Square 03.50 MM (3.38 - 3.67) YELLOW SI Princess IRRADIATED AND/OR HPHT In Stock 0.2500 $2,667.25 $666.81
Square 03.50 MM (3.38 - 3.67) TEAL BLUE SI Princess IRRADIATED AND/OR HPHT In Stock 0.2500 $2,667.25 $666.81
Round 04.10 MM (03.90 - 04.20) .25 CT (.23 - .28) 1/4 TEAL BLUE SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.2500 $2,538.00 $634.50
Round 04.10 MM (03.90 - 04.20) .25 CT (.23 - .28) 1/4 YELLOW SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.2500 $2,538.00 $634.50
ROUND - BLACK 05.20 - 05.90 MM .75 CT (.6990 - .8980) 3/4 BLACK STANDARD Full Cut COLOR ENHANCED In Stock 0.7500 $822.50 $616.88

Shape MM Size Size Ct Color Quality Cut Unique Attribute Availability Wgt Price/Ct Est. Price
Round 03.00 MM (02.81 - 03.10) .10 CT (.088 - .114) 1/10 PINK SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.1000 $5,710.50 $571.05
Square 03.25 MM (3.19 - 3.37) TEAL BLUE SI Princess IRRADIATED AND/OR HPHT In Stock 0.2300 $2,244.25 $516.18
Round 02.80 MM (02.74 - 02.80) .08 CT (.077 - .087) PINK SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.0800 $5,710.50 $456.84
Round 03.80 MM (03.55 - 04.00) .20 CT (.18 - .22) 1/5 YELLOW SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.2000 $2,244.25 $448.85
Round 03.80 MM (03.55 - 04.00) .20 CT (.18 - .22) 1/5 TEAL BLUE SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.2000 $2,244.25 $448.85
Round 03.40 MM (03.24 - 03.54) .15 CT (.135 - .174) 1/6 AQUA BLUE SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.1500 $2,937.50 $440.63
Round 03.40 MM (03.24 - 03.54) .15 CT (.135 - .174) 1/6 PURPLE SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.1500 $2,937.50 $440.63
Round 03.80 MM (03.55 - 04.00) .20 CT (.18 - .22) 1/5 APPLE GREEN SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.2000 $2,185.50 $437.10
Round 03.80 MM (03.55 - 04.00) .20 CT (.18 - .22) 1/5 GARNET RED SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.2000 $2,185.50 $437.10
ROUND - BLACK 04.50 - 05.50 MM .50 CT (.4490 - .6980) 1/2 BLACK STANDARD Full Cut COLOR ENHANCED In Stock 0.5500 $740.25 $407.14
Round 03.80 MM (03.55 - 04.00 .20 CT (.18 - .22) 1/5 DARK GREEN SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.2000 $1,762.50 $352.50
Round 03.80 MM (03.55 - 04.00) .20 CT (.18 - .22) 1/5 BURNT ORANGE SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.2000 $1,762.50 $352.50
Round 03.20 MM (03.11 - 03.23) .12 CT (.115 - .134) 1/8 AQUA BLUE SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.1200 $2,608.50 $313.02
Round 03.20 MM (03.11 - 03.23) .12 CT (.115 - .134) 1/8 PURPLE SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.1200 $2,596.75 $311.61
Square 03.00 MM (2.88 - 3.18) YELLOW SI Princess IRRADIATED AND/OR HPHT In Stock 0.1700 $1,797.75 $305.62


Shape MM Size Size Ct Color Quality Cut Unique Attribute Availability Wgt Price/Ct Est. Price
Square 03.00 MM (2.88 - 3.18) TEAL BLUE SI Princess IRRADIATED AND/OR HPHT In Stock 0.1700 $1,797.75 $305.62
ROUND - BLACK 04.30 - 04.70 MM .37 CT (.3790 - .4480) 3/8 BLACK STANDARD Full Cut COLOR ENHANCED In Stock 0.4100 $705.00 $289.05
Round 02.70 MM (02.51 - 02.73) .07 CT (.067 - .076) PINK SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.0700 $3,983.25 $278.83
Round 03.40 MM (03.24 - 03.54) .15 CT (.135 - .174) 1/6 APPLE GREEN SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.1500 $1,821.25 $273.19
Round 03.40 MM (03.24 - 03.54) .15 CT (.135 - .174) 1/6 GARNET RED SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.1500 $1,821.25 $273.19
Round 03.00 MM (02.81 - 03.10) .10 CT (.088 - .114) 1/10 AQUA BLUE SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.1000 $2,608.50 $260.85
Round 03.00 MM (02.81 - 03.10) .10 CT (.088 - .114) 1/10 PURPLE SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.1000 $2,596.75 $259.68
Round 02.50 MM (02.44 - 02.50) .06 CT (.056 - .066) PINK SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.0600 $3,983.25 $239.00
Round 03.40 MM (03.24 - 03.54) .15 CT (.135 - .174) 1/6 TEAL BLUE SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.1500 $1,527.50 $229.13
Round 03.40 MM (03.24 - 03.54) .15 CT (.135 - .174) 1/6 YELLOW SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.1500 $1,527.50 $229.13
ROUND - BLACK 04.00 - 04.50 MM .33 CT (.2890 - .3780) 1/3 BLACK STANDARD Full Cut COLOR ENHANCED In Stock 0.3300 $669.75 $221.02
Round 03.40 MM (03.24 - 03.54) .15 CT (.135 - .174) 1/6 DARK GREEN SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.1500 $1,445.25 $216.79
Round 03.40 MM (03.24 - 03.54) .15 CT (.135 - .174) 1/6 BURNT ORANGE SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.1500 $1,445.25 $216.79
Round 02.80 MM (02.74 - 02.80) .08 CT (.077 - .087) AQUA BLUE SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.0800 $2,608.50 $208.68
Round 02.80 MM (02.74 - 02.80) .08 CT (.077 - .087) PURPLE SI Full Cut IRRADIATED AND/OR HPHT In Stock 0.0800 $2,596.75 $207.74

 

With the announcement in March 1999 by General Electric and Lazare Kaplan International (LKI) at color-improved High Pressure-High Temperature (HPHT)-treated diamonds were hitting the market, the major gemological laboratories in Europe and the U.S. launched a surge of research initiatives. In fact, from the fall of 1999 to the winter of 2000, there were articles on HPHT-treated diamonds in each of six consecutive issues of the GIA journal Gems & Gemology. In an effort to determine how best to identify HPHT-treated diamonds, the De Beers organization has also been very active in researching the HPHT diamond annealing process. This work is a collaboration between the Diamond Trading Company (DTC) Research Centre, Maidenhead, United Kingdom, and De Beers Industrial Diamonds’ Laboratory in Johannesburg, South Africa. The Maidenhead laboratory’s sophisticated spectroscopic equipment and expertise in characterization, combined with the Johannesburg laboratory’s access to industrial diamond synthesis presses and expertise in high-pressure engineering, has led to substantial progress. Detailed characterization research carried out at the DTC Research Centre and at some of the major gemological laboratories has led to the discovery of a number of features that can indicate HPHT treatment. Techniques include ultraviolet/visible and infrared absorption spectroscopy and, most importantly, laser-excited photoluminescence (PL) spectroscopy, which requires the sample to be cooled with liquid nitrogen to a temperature of –196°C. The latter technique is particularly important for type II diamonds because it is such a highly sensitive technique. Type II diamonds are very pure and highly sensitive measurements are required to detect the very low concentrations of defects that they contain. Several of the major gem-testing laboratories have invested in this sophisticated PL equipment and are therefore in a position to identify the vast majority of HPHT-treated diamonds. Inventing the Tools One of the roles of the DTC Research Centre, in support of the De Beers Gem Defensive Programme , is to assist gem-testing laboratories by developing practical instruments to deal with complex identification problems. To this end, a low-cost, easy-to-use instrument, currently in prototype form, is being developed for rapid screening of potentially HPHT- treated type II diamonds . This instrument will not replace the sophisticated laboratory equipment but it will greatly reduce the number of stones that will need to be examined in such a time-consuming way. Another role of the DTC Gem Defensive Programme is to anticipate future developments in treatment techniques (and also diamond synthesis techniques) that could challenge current identification methods, and to research new techniques that will continue to enable reliable identification to take place. Initially, research both by De Beers and the major gemological laboratories concentrated on areas of current commercial concern. In this area, detection criteria have been firmly established. The initial work has now developed into investigation of wider ranges of starting material, and treatment conditions in which identification may be more subtle. This forward-looking research is currently a very active area for De Beers scientists. No Magic Box So where do we stand at present in terms of the practicalities of detection? There certainly is no magic “black box” that can tell an HPHT- treated stone from an untreated stone with 100 percent accuracy. But this would be an unrealistic expectation. Apart from the relatively trivial task of distinguishing diamonds from simulants, no gemological identification task can be achieved with a single, simple, fully automatic technique. The question is, can procedures and, where appropriate, instrumentation be developed that will allow sufficient numbers of stones to be examined cost effectively so as to address the concerns of the trade? The sophisticated PL equipment that is now in use in the major gem laboratories can identify the vast majority of HPHT- treated diamonds but there will always be a small proportion for which the identification is uncertain. There will also be a small proportion of untreated stones that may be misidentified as treated. With a material as complex and varied as natural diamond such problems are inevitable. Is the PL equipment so expensive and the measurement so time consuming as to be of little use in practice? It is certainly true that the need to make such measurements has greatly increased the workload of gem laboratories and has led to increased delays in having stones graded. But practical means of screening diamonds to reduce the number that need to be looked at in detail are being developed and implemented in grading laboratories. The fact that laboratories are willing to invest in such equipment demonstrates their determination to achieve the best results possible and so maintain the integrity of natural, untreated diamonds. Will future developments in treatments invalidate the identification techniques? The honest answer, of course, is that one cannot be sure. But both De Beers and those gem laboratories that carry out research are committing considerable resources to address this issue. Three years ago, HPHT treatment was generally believed to be undetectable. The fact that this is certainly not the case today demonstrates what can be achieved in a relatively short time by dedicated research. Practical Advice What practical advice can be offered to the trade to help identify potentially HPHT-treated diamonds? Fancy yellow, greenish-yellow, pink and blue diamonds need to be referred to a suitably equipped gem-testing laboratory. For greenish-yellow diamonds, intense green fluorescence isa good indication that the stone may be HPHT treated but, ultimately, laboratory examination will be required. Colorless and near-colorless diamonds should first be checked to see if they are transparent to ultraviolet (UV) radiation, and are therefore likely to be type II. This is accomplished using a short-wave UV lamp and a UV- sensitive phosphor — simple equipment that is commercially available. Colorless and near-colorless diamonds that are UV transparent should be referred to a suitably equipped gem-testing laboratory. What about diamonds that are too small to be cost effectively submitted to a gem-testing laboratory? Colorless and near-colorless stones can still be checked to see if they are UV transparent or opaque. Those that are UV opaque will be type I and therefore unlikely to have been treated. Forthe very small proportion of diamonds that are UV transparent and therefore likely to be type II, the only realistic option is to insist upon a written declaration from the supplier that the stones are natural and untreated. For fancy yellow, greenish-yellow, pink and blue diamonds, the same written declaration should be insisted upon. The Rules In the U.S., the Federal Trade Commission Guides §23.22 state that “it is unfair or deceptive to fail to disclose that a gemstone has been treated if … the treatment has a significant effect on the stone’s value. The seller should disclose that the gemstone has been treated. Note to §23.22: The disclosures outlined in this section are applicable to sellers at every level of the trade.” The rules of the International Jewellery Confederation (CIBJO) state in Article 6.1 of the CIBJO Diamond Book that “if the natural color of a diamond has been artificially altered, it has to be clearly declared as ‘treated,’ ‘artificially colored, or ‘irradiated.’” In support of this position, the DTC requires all its sightholders to abide by its Best Practice Principles, which state, “We are committed to the highest industry ethics including the following: …full disclosure at all levels of the diamond distribution chain and, most importantly, to consumers, of all treatments to natural diamonds and compliance with rules, regulations and guidelines published from time to time by the diamond industry’s governing bodies.” How HPHT Works Brown diamonds, both type I and type II, as part of their geological history have been subjected to mechanical stresses at elevated temperatures while deep within the earth. This causes their crystal lattices to become deformed — a process known as plastic deformation. This process introduces linear defects into the crystal, which are known as dislocations. The brown color is associated with the presence of these dislocations. When the diamond crystal is subjected to very high temperatures, the structure of the dislocations is modified, causing the brown coloration to be reduced. At these very high temperatures, diamonds will convert to graphite unless very high pressure is applied. This is done using the same kind of equipment as is used for diamond synthesis, e.g., the conventional “belt” presses developed by General Electric, the cubic or prismatic presses used by NovaTech or the BARS presses developed in Russia. Such equipment is complex and relatively expensive. Typical HPHT conditions can be in excess of 2000ºC and 60,000 atmospheres. Use of such extreme conditions is not without its dangers. Diamonds with inclusions and fractures can be broken and surfaces can become frosted and pitted. Type I diamonds contain nitrogen as a major impurity, typically present at levels of several hundred parts per million. Type II diamonds are extremely pure, with nitrogen concentrations of less than about one part per million. A very small proportion of type II diamonds are classified as type IIb, due to the presence of trace amounts of boron impurities, which give rise to a blue color. In type IIa diamonds (i.e., those type II diamonds that are not type IIb), if the brown coloration is reduced sufficiently by HPHT treatment, the result is a colorless, near-colorless or sometimes a pink diamond. Less than 1 percent of natural diamonds are type II of adequate quality to be suitable for HPHT treatment. In brown or brownish-gray type IIb diamonds, which are of course extremely rare, a pale blue color can be produced by HPHT treatment. In brown type I diamonds, HPHT treatment produces particular nitrogen-containing defects which give rise to a fancy yellow to greenish-yellow color, often with strong green fluorescence.

Diamond enhancements are specific treatments, performed on natural diamonds (usually those already cut and polished into gems), which are designed to improve the gemological characteristics — and therefore the value — of the stone in one or more ways. These include clarity treatments such as laser drilling to remove inclusions, application of sealants to fill cracks, color treatments to improve a white diamond's color grade, and treatments to give fancy color to a white or off-color diamond.

The CIBJO and government agencies such as the United States Federal Trade Commission explicitly require the disclosure of most diamond treatments at the time of sale. Some treatments, particularly those applied to clarity, remain highly controversial within the industry — this arises from the traditional notion that diamond holds a unique or "sacred" place among the gemstones, and should not be treated too radically, if for no other reason than a fear of damaging consumer confidence.

Treated diamonds usually trade at a significant discount to untreated diamonds. This is due to several factors, including relative scarcity — a much larger number of stones can be treated to reach gem quality than are found naturally occurring in a gem quality state — and the potential impermanence of various treatments. Therefore, it is unusual to see a diamond with good overall gemological characteristics undergo treatment. Diamonds which are chosen for treatment are usually those that would be otherwise difficult to sell as gem diamonds, where inclusions or fractures noticeably detract from the beauty of the diamond to even casual observers. In these cases, the loss in value due to treating the diamond is more than offset by the value added by the mitigating of obvious flaws.
Color enhancementsSee also: diamond color
This section needs additional citations for verification.
Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (July 2010)

Generally there are three major methods to artificially alter the color of a diamond: irradiation with high-energy subatomic particles; the application of thin films or coatings; and the combined application of high pressure and high temperature (HPHT). However, there is recent evidence that fracture filling is not only used to improve clarity, but that it can be used for the sole purpose to change the color into a more desirable color as well.[1]

The first two methods can only modify color, usually to turn an off-color Cape series stone (see Material properties of diamond: Composition and color) into a more desirable fancy-colored stone. Because some irradiation methods produce only a thin "skin" of color, they are applied to diamonds that are already cut and polished. Conversely, HPHT treatment is used to modify and remove color from either rough or cut diamonds—but only certain diamonds are treatable in this manner. Irradiation and HPHT treatments are usually permanent insofar as they will not be reversed under normal conditions of jewelry use, whereas thin films are impermanent.

[edit] Irradiation
Pure diamonds, before and after irradiation and annealing. Clockwise from left bottom: 1) Initial (2×2 mm) 2-4) Irradiated by different doses of 2-MeV electrons 5-6) Irradiated by different doses and annealed at 800 °C.Sir William Crookes, a gem connoisseur as well as a chemist and physicist, was the first to discover radiation's effects on diamond color when in 1904 he conducted a series of experiments using radium salts. Diamonds enveloped in radium salt slowly turned a dark green; this color was found to be localized in blotchy patches, and it did not penetrate past the surface of the stone. The emission of alpha particles by the radium was responsible. Unfortunately radium treatment also left the diamond strongly radioactive, to the point of being unwearable.[2] A diamond octahedron so treated was donated by Crookes to the British Museum in 1914, where it remains today: it has lost neither its color nor radioactivity.

Presently diamonds are safely irradiated in four ways: proton and deuteron bombardment via cyclotrons; gamma ray bombardment via exposure to cobalt-60; neutron bombardment via the piles of nuclear reactors; and electron bombardment via Van de Graaff generators. These high-energy particles physically alter the diamond's crystal lattice, knocking carbon atoms out of place and producing color centers. Irradiated diamonds are all some shade of green, black, or blue after treatment, but most are annealed to further modify their color into bright shades of yellow, orange, brown, or pink. The annealing process increases the mobility of individual carbon atoms, allowing some of the lattice defects created during irradiation to be corrected. The final color is dependent on the diamond's composition and the temperature and length of annealing.

Cyclotroned diamonds have a green to blue-green color confined to the surface layer: they are later annealed to 800 °C to produce a yellow or orange color. They remain radioactive for only a few hours after treatment, and due to the directional nature of the treatment and the cut of the stones, the color is imparted in discrete zones. If the stone was cyclotroned through the pavilion (back), a characteristic "umbrella" of darker color will be seen through the crown (top) of the stone. If the stone was cyclotroned through the crown, a dark ring is seen around the girdle (rim). Stones treated from the side will have one half colored deeper than the other. Cyclotron treatment is now uncommon.

Gamma ray treatment is also uncommon, because although it is the safest and cheapest irradiation method, successful treatment can take several months. The color produced is a blue to blue-green which penetrates the whole stone. Such diamonds are not annealed. The blue color can sometimes approach that of natural Type IIb diamonds, but the two are distinguished by the latter's semiconductive properties. As with most irradiated diamonds, most gamma ray-treated diamonds were originally tinted yellow; the blue is usually modified by this tint, resulting in a perceptible greenish cast.

The two most common irradiation methods are neutron and electron bombardment. The former treatment produces a green to black color that penetrates the whole stone, while the latter treatment produces a blue, blue-green, or green color that only penetrates about 1 millimeter deep. Annealing of these stones (from 500–900 °C for neutron-bombarded stones and from 500–1200 °C for electron-bombarded stones) produces orange, yellow, brown, or pink. Blue to blue-green stones that are not annealed are separated from natural stones in the same manner as gamma ray-treated stones.

Prior to annealing, nearly all irradiated diamonds possess a characteristic absorption spectrum consisting of a fine line in the far red, at 741 nm — this is known as the GR1 line and is usually considered a strong indication of treatment. Subsequent annealing usually destroys this line, but creates several new ones; the most persistent of these is at 595 nm.

It should be noted that some irradiated diamonds are completely natural. One famous example is the Dresden Green Diamond. In these natural stones the color is imparted by "radiation burns" in the form of small patches, usually only skin deep, as is the case in radium-treated diamonds. Naturally irradiated diamonds also possess the GR1 line. The largest known irradiated diamond is the Deepdene.
 

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