Diamond color

Last updated

A chemically pure and structurally perfect diamond is perfectly transparent with no hue, or color. However, in reality almost no gem-sized natural diamonds are absolutely perfect. The color of a diamond may be affected by chemical impurities and/or structural defects in the crystal lattice. Depending on the hue and intensity of a diamond's coloration, a diamond's color can either detract from or enhance its value. For example, most white diamonds are discounted in price when more yellow hue is detectable, while intense pink diamonds or blue diamonds (such as the Hope Diamond) can be dramatically more valuable. Of all colored diamonds, red diamonds are the rarest. The Aurora Pyramid of Hope displays a spectacular array of naturally colored diamonds, including red diamonds.

Contents

History of color grading

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. Without any co-operative development, these early grading systems lacked standard nomenclature and consistency. Some early grading scales were; I, II, III; A, AA, AAA; A, B, C. Numerous terms developed to describe diamonds of particular colors: golconda, river, jagers, cape, blue white, fine white, gem blue, brown, etc.

Possible colors

The Hope Diamond, 45.52 carats (9.104 g), dark grayish-blue The Hope Diamond - SIA.jpg
The Hope Diamond, 45.52 carats (9.104 g), dark grayish-blue
Jewellers diamonds in groups of similar colors.
These from the National Museum of Natural History are a medium brown color. National Museum of Natural History Gold Colored Diamonds.JPG
Jewellers diamonds in groups of similar colors. These from the National Museum of Natural History are a medium brown color.
The 296 gems of the Aurora Pyramid of Hope as exhibited in the Natural History Museum in London under natural light. Aurora Pyramid of Hope.jpg
The 296 gems of the Aurora Pyramid of Hope as exhibited in the Natural History Museum in London under natural light.

Diamonds occur in a variety of colors—steel gray, white, blue, yellow, orange, red, green, pink to purple, brown, and black. [1] [2] Colored diamonds contain interstitial impurities or structural defects that cause the coloration; pure diamonds are perfectly transparent and colorless. Diamonds are scientifically classed into two main types and several subtypes, according to the nature of impurities present and how these impurities affect light absorption.

Type I

Type I diamonds have nitrogen atoms as the main impurity, commonly at a concentration of 0.1%. 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). About 98% of gem diamonds are type Ia, and most of these are a mixture of IaA and IaB material: these diamonds belong to the Cape series, named after the diamond-rich region formerly known as Cape Province in South Africa, whose deposits are largely Type Ia. If the nitrogen atoms are dispersed throughout the crystal in isolated sites (not paired or grouped), they give the stone an intense yellow or occasionally brown tint (Type Ib); the rare canary diamonds belong to this type, which represents only 10% of known natural diamonds. Synthetic diamond containing nitrogen is Type Ib. Type I diamonds absorb in both the infrared and ultraviolet region, from 320 nm (3.2×10−7 m). They also have a characteristic fluorescence and visible absorption spectrum (see Optical properties of diamond). [3]

Type II

Type II diamonds have no measurable nitrogen impurities. Type II diamonds absorb in a different region of the infrared, and transmit in the ultraviolet below 225 nm (2.25×10−7 m), unlike Type I diamonds. 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 [4] arising through plastic deformation during crystal growth—these diamonds are rare (1.8% of gem diamonds), but constitute a large percentage of Australian production. Type IIb diamonds, which account for 0.1% of gem diamonds, are usually light blue due to scattered boron within the crystal matrix; these diamonds are also semiconductors, unlike other diamond types (see Electrical properties of diamond). However, a blue-grey color may also occur in Type Ia diamonds and be unrelated to boron. [5] Also not restricted to type are green diamonds, whose color is caused by GR1 color centers in the crystal lattice produced by exposure to varying quantities of radiation. [3]

Pink and red are caused by plastic deformation of the crystal lattice from temperature and pressure. Black diamonds are caused by microscopic black or gray inclusions of other materials such as graphite or sulfides and/or microscopic fractures. Opaque or opalescent white diamonds are also caused by microscopic inclusions. [6] Purple diamonds are caused by a combination of crystal lattice distortion and high hydrogen content. [7]

Colorless diamonds

The majority of mined diamonds fall between white and pale yellow or brown; what is known as the normal color range. Diamonds of more intense color (usually yellow, but in some cases red, green or blue) are termed fancy color diamonds. Black diamonds are also fancy color diamonds. All other factors being equal, the most valuable diamonds are those with the least color (appearing white to the eye), and those possessing vivid color ( especially yellow, pink, and blue). Diamonds at the low end of the normal color range, which possess a pale yellow or brown hue, are the least desirable for jewelry. [8] Color is one of the four traditional factors by which a diamond is evaluated (the others being carat weight, clarity, and cut).

Grading the normal color range

Refers to a grading scale for diamonds in the normal color range used by internationally recognized laboratories (GIA & IGI for example). 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. Grading begins with the letter D, (omitting A, B, C) to ensure that there is no confusion with any of the previous terminology that was used prior to the standardization of the color grading scale. While several grading laboratories use the D–Z color scale (most notably: GIA, EGL, and IGI), there is no universal standard for how the grades are applied. The same diamond submitted for grading at two laboratories employing the same color scale nomenclature, will often receive conflicting grades. [9]

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. Accurate color grading can only be performed with diamond unset, as the comparison with master stones is done with diamond placed on its table facet and pavilion side facing upwards ( i.e.  "upside down"— resting on the face one normally looks at). 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.

Diamonds in the normal color range are graded loose (for example F–G).

Diamond color grading scales [10]
GIAStatus:currentAGSStatus:currentAGSStatus:historical: pre 1995CIBJOStatus:currentIDCStatus:currentScan. D.N.Status:currentOld World TermsStatus:historical
grade and description [11] grade and electronic colorimeter scale [12] grade and electronic colorimeter scale [12] grade [13] grade and description [13] grade for .50ct and over [14] grade for under .50ctseries 1 scale [13] series 2 scale [13]
DColorless00–0.4900–0.75Exceptional white +Exceptional white +ColorlessRiverWhiteFinest WhiteJager
E0.50.5–0.99Exceptional whiteExceptional whiteRiver
10.76–1.35
F1.01.0–1.49Rare white +Rare white +Colorless when viewed through the crownTop WesseltonFine White
21.36–2.00
GNear Colorless1.51.5–1.99Rare whiteRare whiteTop Wesselton
H2.02.0–2.4932.01–2.50WhiteWhiteWesseltonWhiteWesselton
I2.52.5–2.9942.51–3.0Slightly tinted whiteSlightly tinted whiteSlightly coloredTop CrystalSlightly tinted whiteCommercial WhiteTop Crystal
J3.03.0–3.4953.01–3.75CrystalTop silver capeCrystal
KFaint Yellow3.53.5–3.99Tinted whiteTinted whiteTop capeTinted whiteTop cape
63.76–4.5Silver cape
L4.04.0–4.49
M4.54.5–4.9974.51–5.50Tinted color 1Tinted colorSlightly colored to coloredCapeTinted colorLight capeCape
NVery Light Yellow5.05.0–5.49Tinted color 2Low Cape
O5.55.5–5.9985.51–7.0Light yellowCapeVery light yellow
P6.06.0–6.49Light yellow
Q6.56.5–6.99
R7.07.0–7.4997.01–8.5
Dark cape
SLight Yellow7.57.5–7.99Tinted color 3Yellow
T8.08.0–8.49
U8.58.5–8.99108.51–10
V9.09.0–9.49
W9.59.5–9.99
X1010+10+
Y
Z

Colored diamonds

Fancy colored diamonds

Under the GIA system, Yellow or brown color diamonds having color more intense than "Z", as well as diamonds exhibiting color other than yellow or brown are considered fancy colored diamonds. These diamonds are graded using separate systems which indicate the characteristics of the color, and not just its presence. These color grading systems are more similar to those used for other colored gemstones, such as ruby, sapphire, or emerald, than they are to the system used for white diamonds. [15]

Colored diamond grading system

Diamond colors more saturated than this scale are known as "fancy color" diamonds. Any light shade of diamond other than Light Yellow or Light Brown automatically falls out of the scale. For instance, a pale blue diamond won't get a "K", "N", or "S" color grade, it will get a Faint Blue, very Light Blue or Light Blue grade.

Laboratories use a list of 27 color hues that span the full spectrum for colored gems and diamonds (Red, Orangish-Red, Reddish-Orange, orange, Yellowish-Orange, Yellow-Orange, Orange-Yellow, Orangish-Yellow, Yellow, Greenish-Yellow, Green-Yellow, Yellow-Green, Yellowish-Green, Green, Bluish-Green, Blue-Green, Green-Blue, Greenish-Blue, Blue, Violetish-Blue, Bluish-Violet, Violet, Purple, Reddish-Purple, Red-Purple, Purple-Red, Purplish-Red). A modifying color combination can also be added (e.g., Olive or Brown-Olive) for stones without the purest hues. Additionally, for diamonds the following colors are used: White (which are milky), Black (which are opaque), Gray, Pink, Brown.

The saturation of these hues is then described with one of nine descriptors: Faint, Very Light, Light, Fancy Light, Fancy, Fancy Dark, Fancy Intense, Fancy Deep, Fancy Vivid.

The terms "Champagne", "Cognac" and "Coffee" refer to different types of brown diamonds. In the diamond processing/dealing industry, the word "Brown" is considered a killer as far as diamond value goes. Even though champagne is a light yellow color, champagne diamonds are Light Brown. Cognac is usually used to describe a diamond that is Orangish-Brown because cognac is a deep golden-orange color. Coffee is usually used to describe a diamond that is a Deep Brown or Vivid Brown color. Some grading agencies may also describe brown stones as Fancy Yellowish-Brown, Fancy Light Brown, Fancy Intense Brown, etc.

Value of colored diamonds

Diamonds that enter the Gemological Institute of America's scale are valued according to their clarity and color. For example, a "D" or "E" rated diamond (both grades are considered colorless) is much more valuable than an "R" or "Y" rated diamond (light yellow or brown). This is due to two effects: high-color diamonds are rarer, limiting supply; and the bright white appearance of high-color diamonds is more desired by consumers, increasing demand. Poor color is usually not enough to eliminate the use of diamond as a gemstone: if other gemological characteristics of a stone are good, a low-color diamond can remain more valuable as a gem diamond than an industrial-use diamond, and can see use in diamond jewelry. Furthermore, it is much more cost effective to purchase a near-colorless grade diamond (e.g. "G" rated) instead of a colorless grade diamond (e.g. "D" rated), as they are nearly indistinguishable to the naked untrained eye, especially when mounted on a ring setting. [16]

Fancy diamonds are valued using different criteria than those used for regular diamonds. When the color is rare, the more intensely colored a diamond is, the more valuable it becomes. Another factor that affects the value of Fancy-Colored diamonds is fashion trends. For example, pink diamonds fetched higher prices after Jennifer Lopez received a pink diamond engagement ring. [17]

Fancy-colored diamonds such as the deep-blue Hope Diamond are among the most valuable and sought-after diamonds in the world. In 2009, a 7-carat (1.4 g) blue diamond fetched the then highest price per carat ever paid for a diamond when it was sold at auction for 10.5 million Swiss francs (US$9.5 million at the time) which is in excess of US$1.3 million per carat. [18] This record was broken in 2013 when an orange diamond sold for US$35 million or US$2.4 million per carat. [19] It was again broken in 2016 when the Oppenheimer Blue, a 14.62-carat (2.924 g) vivid blue diamond became the most expensive jewel ever sold at an auction. [20] It is the largest fancy vivid blue diamond classified by the Gemological Institute of America ever sold at auction; it sold at Christie's in Geneva in May 2016 for US$50.6 million. The record was broken again by the Pink Star diamond on April 3, 2017. The Pink Star was sold at an auction in Hong Kong for US$71.2 m (553 million Hong Kong dollars including fees) to Chow Tai Fook Enterprises.(GBP 34.7m; 56.83m SFr). [21]

See also

Related Research Articles

<span class="mw-page-title-main">Beryl</span> Gemstone: beryllium aluminium silicate

Beryl ( BERR-əl) is a mineral composed of beryllium aluminium silicate with the chemical formula Be3Al2Si6O18. Well-known varieties of beryl include emerald and aquamarine. Naturally occurring, hexagonal crystals of beryl can be up to several meters in size, but terminated crystals are relatively rare. Pure beryl is colorless, but it is frequently tinted by impurities; possible colors are green, blue, yellow, pink, and red (the rarest). It is an ore source of beryllium.

<span class="mw-page-title-main">Diamond</span> Allotrope of carbon often used as a gemstone and an abrasive

Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Another solid form of carbon known as graphite is the chemically stable form of carbon at room temperature and pressure, but diamond is metastable and converts to it at a negligible rate under those conditions. Diamond has the highest hardness and thermal conductivity of any natural material, properties that are used in major industrial applications such as cutting and polishing tools. They are also the reason that diamond anvil cells can subject materials to pressures found deep in the Earth.

<span class="mw-page-title-main">Emerald</span> Green gemstone, a beryl variety

Emerald is a gemstone and a variety of the mineral beryl (Be3Al2(SiO3)6) colored green by trace amounts of chromium or sometimes vanadium. Beryl has a hardness of 7.5–8 on the Mohs scale. Most emeralds are highly included, so their toughness (resistance to breakage) is classified as generally poor. Emerald is a cyclosilicate.

<span class="mw-page-title-main">Gemstone</span> Piece of mineral crystal used to make jewelry

A gemstone is a piece of mineral crystal which, in cut and polished form, is used to make jewelry or other adornments. However, certain rocks and occasionally organic materials that are not minerals are also used for jewelry and are therefore often considered to be gemstones as well. Most gemstones are hard, but some soft minerals are used in jewelry because of their luster or other physical properties that have aesthetic value. Rarity and notoriety are other characteristics that lend value to gemstones.

<span class="mw-page-title-main">Sapphire</span> Gem variety of corundum

Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide (α-Al2O3) with trace amounts of elements such as iron, titanium, chromium, vanadium, or magnesium. The name sapphire is derived from the Latin "saphirus" and the Greek "sapheiros", both of which mean blue. It is typically blue, but natural "fancy" sapphires also occur in yellow, purple, orange, and green colors; "parti sapphires" show two or more colors. Red corundum stones also occur, but are called rubies rather than sapphires. Pink-colored corundum may be classified either as ruby or sapphire depending on locale. Commonly, natural sapphires are cut and polished into gemstones and worn in jewelry. They also may be created synthetically in laboratories for industrial or decorative purposes in large crystal boules. Because of the remarkable hardness of sapphires – 9 on the Mohs scale (the third hardest mineral, after diamond at 10 and moissanite at 9.5) – sapphires are also used in some non-ornamental applications, such as infrared optical components, high-durability windows, wristwatch crystals and movement bearings, and very thin electronic wafers, which are used as the insulating substrates of special-purpose solid-state electronics such as integrated circuits and GaN-based blue LEDs. Sapphire is the birthstone for September and the gem of the 45th anniversary. A sapphire jubilee occurs after 65 years.

<span class="mw-page-title-main">Topaz</span> Silicate mineral

Topaz is a silicate mineral of aluminium and fluorine with the chemical formula Al2SiO4(F,OH)2. It is used as a gemstone in jewelry and other adornments. Common topaz in its natural state is colorless, though trace element impurities can make it pale blue or golden brown to yellow orange. Topaz is often treated with heat or radiation to make it a deep blue, reddish-orange, pale green, pink, or purple.

<span class="mw-page-title-main">Tourmaline</span> Cyclosilicate mineral group

Tourmaline is a crystalline silicate mineral group in which boron is compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. Tourmaline is a gemstone and can be found in a wide variety of colors.

<span class="mw-page-title-main">Ruby</span> Variety of corundum, mineral, gemstone

A ruby is a pinkish red to blood-red colored gemstone, a variety of the mineral corundum. Ruby is one of the most popular traditional jewelry gems and is very durable. Other varieties of gem-quality corundum are called sapphires. Ruby is one of the traditional cardinal gems, alongside amethyst, sapphire, emerald, and diamond. The word ruby comes from ruber, Latin for red. The color of a ruby is due to the element chromium.

<span class="mw-page-title-main">Tanzanite</span> Blue to purple variety of the mineral zoisite

Tanzanite is the blue and violet variety of the mineral zoisite, caused by small amounts of vanadium. Tanzanite belongs to the epidote mineral group. Tanzanite is only found in Simanjiro District of Manyara Region in Tanzania, in a very small mining area near the Mererani Hills.

<span class="mw-page-title-main">Material properties of diamond</span>

Diamond is the allotrope of carbon in which the carbon atoms are arranged in the specific type of cubic lattice called diamond cubic. It is a crystal that is transparent to opaque and which is generally isotropic. Diamond is the hardest naturally occurring material known. Yet, due to important structural brittleness, bulk diamond's toughness is only fair to good. The precise tensile strength of bulk diamond is little known; however, compressive strength up to 60 GPa has been observed, and it could be as high as 90–100 GPa in the form of micro/nanometer-sized wires or needles, with a corresponding maximum tensile elastic strain in excess of 9%. The anisotropy of diamond hardness is carefully considered during diamond cutting. Diamond has a high refractive index (2.417) and moderate dispersion (0.044) properties that give cut diamonds their brilliance. Scientists classify diamonds into four main types according to the nature of crystallographic defects present. Trace impurities substitutionally replacing carbon atoms in a diamond's crystal structure, and in some cases structural defects, are responsible for the wide range of colors seen in diamond. Most diamonds are electrical insulators and extremely efficient thermal conductors. Unlike many other minerals, the specific gravity of diamond crystals (3.52) has rather small variation from diamond to diamond.

Diamond enhancements are specific treatments, performed on natural diamonds, which are designed to improve the visual gemological characteristics of the diamond in one or more ways. These include clarity treatments such as laser drilling to remove black carbon inclusions, fracture filling to make small internal cracks less visible, color irradiation and annealing treatments to make yellow and brown diamonds a vibrant fancy color such as vivid yellow, blue, or pink.

<span class="mw-page-title-main">Diamond simulant</span> Diamond-like object which is not a diamond

A diamond simulant, diamond imitation or imitation diamond is an object or material with gemological characteristics similar to those of a diamond. Simulants are distinct from synthetic diamonds, which are actual diamonds exhibiting the same material properties as natural diamonds. Enhanced diamonds are also excluded from this definition. A diamond simulant may be artificial, natural, or in some cases a combination thereof. While their material properties depart markedly from those of diamond, simulants have certain desired characteristics—such as dispersion and hardness—which lend themselves to imitation. Trained gemologists with appropriate equipment are able to distinguish natural and synthetic diamonds from all diamond simulants, primarily by visual inspection.

The Pumpkin Diamond is a diamond weighing 5.54 carats rated in color as Fancy Vivid Orange by the Gemological Institute of America. While this may seem small when compared to other famous diamonds, the Pumpkin Diamond is, in fact, one of the largest Fancy Vivid Oranges the GIA reports having rated and is unique compared to other orange diamonds because it is light-colored and notably intense. The Pumpkin Diamond was mined in Central African Republic and then imported into South Africa for sale, it was later cut and polished by William Goldberg, and put to auction at Sotheby's where it was bought by Ronald Winston of the House of Harry Winston for the price of $1.3 million. It is currently estimated to be valued at $3 million.

<span class="mw-page-title-main">Diamond (gemstone)</span> Gemstone

Diamond is one of the best-known and most sought-after gemstones. They have been used as decorative items since ancient times.

Diamond type is a method of scientifically classifying diamonds by the level and type of their chemical impurities. Diamonds are separated into five types: Type Ia, Type Ib, Type 1aB, Type IIa, and Type IIb. The impurities measured are at the atomic level within the crystal lattice of carbon atoms and so, unlike inclusions, require an infrared spectrometer to detect.

<span class="mw-page-title-main">Brown diamonds</span> Most common color variety of natural diamonds

Brown diamonds are the most common color variety of natural diamonds. In most mines, brown diamonds account for 15% of production. The brown color makes them less attractive to some people as gemstones, and most are used for industrial purposes. However, improved marketing programs, especially in Australia and the United States, have resulted in brown diamonds becoming valued as gemstones and even referred to as chocolate diamonds.

Graff is a British multinational jeweller based in London. It was founded by British jeweller Laurence Graff in 1960. A vertically integrated company, Graff operations comprise the design, manufacture and retail distribution of jewellery and watches.

<span class="mw-page-title-main">Blue diamond</span> Blue colored variant of a diamond

Blue diamond is a type of diamond which exhibits all of the same inherent properties of the mineral except with the additional element of blue color in the stone. They are colored blue by trace amounts of boron that contaminate the crystalline lattice structure. Blue diamonds belong to a subcategory of diamonds called fancy color diamonds, the generic name for diamonds that exhibit intense color.

<span class="mw-page-title-main">Pink diamond</span> Type of diamond that has pink color

Pink diamond is a type of diamond that has pink color. The source of their pink color is greatly debated in the gemological world but it is most commonly attributed to plastic deformation that these diamonds undergo during their formation.

<span class="mw-page-title-main">Red diamond</span> Rare red-coloured variety of diamond

A red diamond is a diamond which displays red colour and exhibits the same mineral properties as colourless diamonds. Red diamonds are commonly known as the most expensive and the rarest diamond colour in the world, even more so than pink or blue diamonds, as very few red diamonds have been found. Red diamonds, just like pink diamonds, are greatly debated as to the source of their colour, but the gemological community most commonly attributes both colours to gliding atoms in the diamond's structure as it undergoes enormous pressure during its formation. Red diamonds are among the 12 colours of fancy colour diamonds, and have the most expensive price per carat. They will typically run in the hundreds of thousands of dollars per carat range. Since they are the rarest colour, it is difficult to find them in large sizes, and they are mostly found in sizes less than 1 carat. Red diamonds only exist with one colour intensity, Fancy, although their clarities can range from Flawless to Included, just like white diamonds. The largest and most flawless red diamond is the 5.11 carat Fancy Red Moussaieff Red Diamond, which has internally flawless clarity.

References

  1. Fred Cuellar (2005-03-01). How to Buy a Diamond: Insider Secrets for Getting Your Money's Worth . Sourcebooks Casablanca. p.  19. ISBN   978-1-4022-0409-8.
  2. Antoinette Matlins, Antonio C. Bonanno (April 2009). Jewelry & Gems, the Buying Guide: How to Buy Diamonds, Pearls, Colored ... p. 37. ISBN   978-0-943763-71-2.
  3. 1 2 J. Walker (1979). "Optical absorption and luminescence in diamond" (PDF). Rep. Prog. Phys. 42 (10): 1605–1659. Bibcode:1979RPPh...42.1605W. CiteSeerX   10.1.1.467.443 . doi:10.1088/0034-4885/42/10/001. S2CID   250857323.
  4. Mäki, Jussi-Matti; et al. (2009). "Properties of optically active vacancy clusters in type IIa diamond". Journal of Physics: Condensed Matter. 21 (36): 364216. Bibcode:2009JPCM...21J4216M. doi:10.1088/0953-8984/21/36/364216. PMID   21832322. S2CID   24373060.
  5. K. Iakoubovskii; Adriaenssens, G.J (2002). "Optical characterization of natural Argyle diamonds" (PDF). Diamond and Related Materials. 11 (1): 125. Bibcode:2002DRM....11..125I. doi:10.1016/S0925-9635(01)00533-7.
  6. "Color in Diamonds". Natural History Museum of L.A. Minblog. January 21, 2013.
  7. DeMarco, Anthony (September 13, 2014). "3.37-Carat 'Purple Orchid' Diamond To Be Unveiled At Hong Kong Jewelry Show". Forbes.
  8. "Diamond Color" . Retrieved 2020-03-12.
  9. "GIA vs EGL Color Grading in Diamonds" . Retrieved 2020-02-26.
  10. Organizations:GIA – Gemological Institute of America, AGI – Antwerpse Gemologische Instelling, AGS – American Gem Society, CIBJO – Confédération International de la Bijouterie, Joaillerie, Orfèvrerie des Diamantes, Perles et Pierres (World Jewellery Confederation), IDC – International Diamond Council, Scan. D.N. – Scandinavian Diamond Nomenclature
  11. Diamond Grading: Lab Manual Gemological Institute of America, Carlsbad, 2004
  12. 1 2 The AGS Way: Diamond Grading Standards American Gem Society, 1999
  13. 1 2 3 4 Pagel-Thielsen, Verena G.G., F.G.A. Diamond Grading ABC: The Manual Rubin & Son n.v., Antwerp, 9th edition, 2001, ISBN   3-9800434-6-0.
  14. Engagement Diamond FAQ
  15. "Diamonds colour chart". kristallsmolensk.com. Retrieved April 6, 2016.
  16. Naturski, Sebastian. "Diamond Color". Your Diamond Teacher. Retrieved 26 December 2016.
  17. "Shades Of A Desert Rose". Idex. June 22, 2004. Retrieved March 12, 2020.
  18. Nebehay, Stephanie (May 13, 2009). "Corrected: Rare blue diamond sells for record $9.5 million". Reuters . Retrieved September 9, 2009.
  19. O'Brien, Jane (December 24, 2014). "What makes pink diamonds pink?". BBC News.
  20. "Oppenheimer Blue diamond sets new auction record". BBC News Online. 18 May 2016. Retrieved 18 May 2016.
  21. "Oppenheimer Blue diamond sells for world record at auction". The Guardian. 18 May 2016. Retrieved 18 May 2016.

Further reading