Frequently Asked Qustions


What are synthetic diamonds?

Synthetic diamonds have essentially the same chemical composition and crystal structure as natural diamonds but they are grown in a laboratory. In the last 30 years, gem quality synthetic diamonds have been grown in Japan, South Africa, Russia, Ukraine, and the United States. Generally speaking, there are two methods for producing synthetic diamonds: high pressure/high temperature (HPHT) or Chemical Vapor Deposition (CVD).

Synthetic diamonds have been available to consumers since the mid-1980s. While they still represent only a small segment of the market, they are becoming more widespread and increasingly difficult to detect. GIA is at the forefront in meeting this challenge, giving a distinct report for synthetics so that there is no confusion in the marketplace. What are HPHT-treated diamonds?

HPHT, which stands for high pressure/high temperature, is a laboratory process that can permanently alter the color of some diamonds. Scientists began to experiment with this technique in the 1990s. HPHT treatment can decolorize certain types of diamond or give others a variety of attractive colors such as pink, blue, green, or yellow.

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What are HPHT synthetic diamonds?

Synthetic diamonds grown using the high pressure/high temperature (HPHT) method have been produced for decades. This process uses equipment that replicates the intense heat and pressure that create natural diamonds deep inside the earth. HPHT synthetic diamonds have been produced in a variety of colors, including yellow, blue, green, pink, red, and purple, as well as colorless. Physically, optically, and chemically they are nearly identical to their natural counterparts, but these synthetics can be identified by a trained gemologist using standard gem-testing equipment.

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What are CVD diamonds?

Synthetic diamonds produced by the chemical vapor deposition (CVD) process are grown at low pressures and relatively low temperatures. This growth technique can produce thin, brown to near-colorless synthetic diamond crystals that are suitable for faceting for jewelry purposes. Synthetic diamonds grown by this method are considered “purer” than those grown by the traditional HPHT technique, and therefore more difficult to detect.

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What are beryllium-diffused sapphires?

Diffusion is a treatment process that uses heat and chemicals to add an element from an external source into a gemstone to change its color. Even the most perfect crystal has places in its lattice where atoms are missing. These gaps are termed “vacancies.” In the case of corundum, which is made up of aluminum and oxygen atoms, the higher the temperature, the more vacancies there will be. The color change depends on the type of element that is diffused into the corundum, the stone’s inherent chemical composition, and the conditions under which the diffusion process takes place.

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What is a SI3 clarity grade?

GIA has never used this grade and has no plans to use it in the future. If the owner of a diamond has a report from a lab where the SI3 grade was assigned and would like to know how GIA would grade the stone, send the diamond to GIA’s laboratory for a diamond grading report. Please contact the laboratory offices to obtain information about fees and how to submit the diamond: GIA Gem Laboratory, Carlsbad, California, (800) 421-7250, ext. 7590, e-mail:; GIA Gem Laboratory, New York City: (212) 221-5858, e-mail:

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What is GIA's role in the Kimberley Process Certification Scheme?

In 2000, GIA began to work closely with the World Diamond Council as they led the diamond industry's efforts to find ways to stop the illegal flow of conflict diamonds into the international marketplace. GIA's work concentrated on research into diamond composition and origin, testifying on this topic before Congress and participating in a White House Conference on conflict diamonds.

GIA has also been contacted over the years to discuss its research in public forums and the news media. As the work of the diamond industry - along with the United Nations, government and non-government organizations - moved away from the technical side and toward the process of certifying the diamond's path from mine to consumer, GIA's role subsided and became less visible.

Although GIA is not directly involved, the Kimberley Process Certification Scheme is fully supported and its principles upheld. GIA's role is now largely behind-the-scenes, serving as an engaged observer of the issue and remaining supportive of the Kimberley Process.

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How can I locate a qualified appraiser?

A GIA Diamond Grading Report offers technical information on the dimensions, quality, and identifying characteristics of a loose diamond but does not provide an appraised value. This service is performed by an independent appraiser. An appraisal should contain a quality analysis, description, and valuation of the jewelry item. To locate an appraiser, check your local phone listings or contact an appraisal association.

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Where can I find dealers or suppliers?

GIA is a nonprofit institution dedicated to serving the jewelry industry through education and research, and must remain impartial by not recommending or endorsing dealers or suppliers. However, there are several independently published directories that contain this type of information. These directories are organized by the type of product (e.g. finished jewelry, loose stones, services, etc.), followed by a list of dealers under each category (e.g. emerald, ruby, etc.). The address information for each dealer is available alphabetically by company name in the back of the issue.

Jewelers' Circular Keystone, a jewelry trade magazine known as JCK, publishes a directory issue each January that lists many wholesalers and dealers. Their website is To order the JCK directory issue, visit or call (646) 746-6456.

Lapidary Journal, a popular magazine for gem cutters, publishes an issue each May called the Annual Buyers' Directory. In this issue, they list products, services, and suppliers of gems and jewelry. Their website is You can purchase the directory by visiting or call (610) 964-6300.

Colored Stone magazine publishes a show guide in listing exhibitors for the Tucson gem shows each February. Visit or, or call (610) 964-6300.

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Can I purchase a diamond price list?

GIA is not involved in pricing, but there are several independent companies that do publish wholesale price lists. These price lists are available to the jewelry trade only.

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Do you have a list of auctioneers that buy or sell estate jewelry?

This page provides a list of major auction firms.

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Where are the majority of diamonds found in the world?

2003 Diamond Production
Countries Total Carats: Total Value:
Botswana 30,500,000 $2,521,000,000
Russia 33,000,000 $1,650,000,000
Canada 11,200,000 $1,235,000,000
South Africa 12,700,000 $1,063,000,000
Angola 5,700,000 $900,000,000
D.R. Congo 25,000,000 $600,000,000
Australia 30,900,000 $450,000,000
Nambia 1,500,000 $450,000,000
Other Producers 4,500,000 $371,000,000
World Total 155,000,000 $9,240,000,000

Diamond production figures can be calculated by total carat weight or total value of the diamonds mined.

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Is your library open to the public?

Any person or company can contact the library for quick reference information either by e-mail (, traditional correspondence, fax (760) 603-4256, or you can come to the library and do your own research in the library’s study areas. To contact the library by phone, please use the following numbers: (800) 421-7250 ext. 4046 or 4068, (760) 603-4046, (760) 603-4068. These extensions are answered Monday through Friday from 7:30 a.m. - 5:00 p.m., Pacific Time.

You will be given detailed citations and, if possible, contact information in order to obtain the magazine issue, journal issue, or book you request. No interlibrary loan service is provided except to the library’s own employees. Due to copyright restrictions, GIA does not own the copyright to the majority of the information that the library carries and cannot mail photocopies.

If there is a reference you need in GIA’s quarterly journal, Gems & Gemology, the subscriptions department will send you the issue or fax a copy of the article for a fee (the articles are not available electronically). Until you know exactly which issue or article you need, it's best to start your search with the library.

Only GIA employees and students attending classes at the Carlsbad campus can check-out materials from the library. If you attend extension classes on GIA’s Carlsbad campus, you will have limited check-out privileges for the time that you are enrolled. All other customers, including Distance Education students, may view the materials in the library's study areas as long as a current photo ID is presented. The GIA library is a closed-stack library which means all non-GIA employees are served from the front counter. Currently, the card catalog is not available on the Internet.

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I found a clear, colorless stone that scratches glass. I think it might be a diamond, but how can I find out for sure?

The stone you found could be a number of things. Many minerals form as colorless crystals. Nor is the scratch test sufficient proof that the stone is a diamond. Anything that has a hardness equal to or higher than glass, which ranges from 5 to 6 on the Mohs hardness scale, can scratch glass. Additional gemological tests need to be performed to provide a positive identification.

The GIA laboratory offers a range of gem identification services. Call (800) 421-7250, ext. 7590, for information on submitting a stone. You can also have a gemologist in your area help you identify the stone. To find a GIA graduate gemologist, search the GIA Alumni Directory online or check your local yellow pages for any jewelers in your area that advertise that they have a gemologist on staff. Also, any jeweler that belongs to the American Gem Society (AGS) will have a trained gemologist on staff.

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How can I tell moissanite apart from a diamond?

Synthetic moissanite is a diamond stimulant with properties are much different from those of diamond.  An experienced gemologist will be able to distinguish between the two. If there is any doubt, the stone can be sent to a qualified independent laboratory for identification.

Synthetic moissanite has a lower specific gravity than diamond and will float in methylene iodide. Under magnification, look for the following characteristics: doubling in appearance of facet junctions and inclusions of whitish or reflective needles.

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What is fluorescence? Is it something I should be concerned about?

Fluorescence is visible light that is emitted after a gem is exposed to ultraviolet (UV) radiation. This phenomenon occurs in some diamonds and other gemstones. The fluorescence that occurs naturally in a diamond arises from submicroscopic structures within the diamond when it is exposed to UV light.

On GIA’s diamond grading reports, the strength of the fluorescence is noted as none, faint, medium, strong, or very strong. Beginning with medium, the color of the fluorescence will be noted (blue, yellow, green, etc.). If fluorescence is faint, the report will not indicate the color. Blue is by far the most common fluorescence color in diamonds.

Some jewelers consider fluorescence an undesirable characteristic. However, GIA's research indicated that fluorescence can have a positive effect by making a diamond appear whiter.

Some treatments can alter the fluorescence of a diamond. For more information on this, please follow the links on GIA’s HPHT treatment page.

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What is an "Ideal" Cut?

There was a time when GIA courses promoted the concept of "ideal” proportions. Yet subsequent technological advances have allowed more exact testing of cut diamonds in the area of brilliance and "fire." These studies showed that in reality there is a wide range of proportion parameters that yield an attractive, appealing diamond. This change in thinking also takes into consideration that people have different tastes and preferences; if shown a number of diamonds cut with various proportion combinations that display high degrees of brilliancy and fire, they will have varying opinions on which is the most beautiful. The term "ideal" suggests a single set of exact proportions, which is unrealistic. Therefore, "ideal cut" is not an authoritative term.

On the GIA website, in the GIA Research section, you will find a series of short articles titled "GIA on Diamond Cut." These articles explain the basis of the cut research and discuss key issues in the evaluation of proportions for round brilliant cut diamonds.

GIA’s cut grading system for round brilliant diamonds was incorporated into GIA's curriculum and laboratory grading services in 2005. Return to Top

What are the 4Cs?

  • Carat Weight
  • Color
  • Clarity
  • Cut

The Four C’s—Carat Weight, Color, Clarity, and Cut —are the essential characteristics of diamond quality. GIA developed the Four C’s during the mid-twentieth century.

Carat Weight: The metric carat, which equals 0.200 grams, is the standard unit of weight for diamonds and all other gems besides pearls. If other factors are equal, a stone that weighs more will be more valuable.

Color: Grading color in the normal range involves deciding how closely a stone's bodycolor approaches colorlessness. Most diamonds have at least a trace of yellow or brown. With the exception of some fancy–color diamonds—ones that are naturally blue, pink, purple, or red, for instance—the colorless grade is the most valuable. Click here for more information on Color Grading.

Clarity: Clarity is the measure of a diamond’s internal inclusions external blemishes. The size, number, position, nature, and color or relief of these characteristics determines the clarity grade. The GIA Clarity Scale ranges from Flawless to Imperfect. Very few diamonds are Flawless, showing no inclusions or blemishes when examined by a skilled grader under 10× magnification. If all other factors are equal, Flawless stones are the most valuable. Click here for more information on Clarity Grading.

Cut: The proportions and finish of a polished diamond are its cut, or “make.” (Cut can also mean the diamond’s shape, as in an emerald cut or a marquise cut.) Proportions are the size and angle relationships between the facets and different parts of the stone. Finish includes polish and details of facet shape and placement. Cut affects both the weight yield from rough and the optical efficiency of the polished stone; the more successful the cutter is in balancing these considerations, the more valuable the stone will be.

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What is the GIA Clarity Scale for diamonds?

Diamonds have internal features, called inclusions, and surface irregularities, called blemishes. Together, these are a diamond’s clarity characteristics. A clarity grade is determined by the relative absence of clarity characteristics.

Flawless (FL): no blemishes or inclusions when examined by a skilled grader under 10× magnification.

Internally Flawless (IF): no inclusions when examined by a skilled grader, and only insignificant blemishes under 10×.

Very, Very Slightly Included (VVS1 and VVS2): contain minute inclusions that are difficult for even a skilled grader to locate under 10×. VVS1: extremely difficult to see, visible only from the pavilion or small and shallow enough to be removed by minor repolishing. VVS2: very difficult to see.

Very Slightly Included (VS1 and VS2): contain minor inclusions ranging from difficult (VS1) to somewhat easy (VS2) for a trained grader to see under 10×.

Slightly Included (SI1 and SI2): contain noticeable inclusions that are easy (SI1) or very easy (SI2) to see under 10×. In some SI diamonds, inclusions can be seen with the unaided eye.

Included (I1, I2, I3): contain inclusions that are obvious to a trained grader under 10×, can often be easily seen face-up with the unaided eye, potentially affect the stone's durability, or are so numerous they affect transparency and brilliance.

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What is a Diamond Grading Report?

In 1955, GIA revolutionized the industry with its Diamond Grading Report. Based on the 4Cs and GIA’s International Diamond Grading System™, the report provides a comprehensive analysis of quality and authenticity for diamonds in the D-to-Z color range. It contains information on shape and cutting style, measurements and weight, proportions and finish, as well as grades for clarity, color, and cut. The GIA Diamond Grading Report has earned a reputation for unrivaled accuracy and integrity.

For stones between 0.18 and 1.99 carats, GIA offers the GIA Diamond Dossier®. It contains the same information found on the traditional report in a more compact format. As an added security measure, the GIA Diamond Dossier® includes a laser inscription of the identification number.

GIA’s laser inscription service can also be used for personal messages and anniversary dates. Visible with 10x magnification, a laser inscription can be placed on the girdle of a diamond as small as 0.18 carats. The procedure causes no damage and does not affect the stone’s color or clarity.

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What is the GIA Diamond Dossier®?

The GIA Diamond Dossier, introduced in 1998, is a grading report for loose diamonds between 0.15 and 1.99 carats. It offers the same type of information as GIA’s traditional grading reports, only in a smaller format. The service also includes a laser-inscribed report number.

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What are Colored Diamonds?

While most diamonds occur in the colorless to light yellow range, some have a natural color that is deep and distinct. These are known as fancy-color diamonds. Unlike colorless and near-colorless diamonds, which are valued for their lack of color, fancies are valued for the strength of their color. Colored diamonds are a small but increasingly popular segment of the diamond market.

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Why are Colored Diamonds gaining so much popularity?

In the past two decades, colored diamonds have enjoyed greater popularity than ever before. There was a turning point in the 1970s when revolutionary new cutting styles emerged for fancy color diamonds. Rather than emphasizing brilliance and fire, the virtues sought in near-colorless diamonds, these cuts emphasize color intensity. As fancy color diamonds began to reach the market, the Argyle mine in Western Australia launched a marketing campaign that helped changed the public’s perception of these previously overlooked diamonds. The 1987 sale of the Hancock Red, at a record auction price of $926,000 per carat, was another milestone that nudged the popularity of fancy coloreds.

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How are Fancies Color Graded?

GIA’s system for color-grading colored diamonds was developed in the mid-1950s and revamped in the mid-1990s. The system expresses color using the attributes of hue (the characteristic color), tone (the color’s relative lightness or darkness), and saturation (the strength or weakness of the color). Using controlled viewing conditions and color comparators, the grader determines the stone’s color from one of 27 hues. The fancy grade describes the stone’s tone and saturation with romantic names like “Fancy Light,” “Fancy Intense,” and “Fancy Vivid.”

Today, the GIA color grading system for colored diamonds is used worldwide. Many of the most famous colored diamonds, including the blue Hope, the Dresden Green, and the Hancock Red, have been examined by the GIA laboratory.

GIA offers two types of grading reports for colored diamonds. The GIA Colored Diamond Grading Report contains the same comprehensive information as the GIA Diamond Grading Report. In addition, the GIA Colored Diamond Identification and Origin Report, known as the color-only report, gives a color grade and the nature of the color.

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