Q: What is a diamond?
A diamond is a mineral composed essentially of carbon crystallized at extremely high temperatures and pressures; in nature, diamonds form 150 to 200 kilometers (93 to 124 miles) or more below the earth’s surface. Diamond is the hardest of all known natural substances (10 on the Mohs Hardness Scale). It is 2.417, dispersion 0.044, specific gravity 3.52, and its luster is adamantine. Diamond forms in the cubic, or isometric, crystal system, has four directions of perfect octahedral cleavage, and shows a step-like fracture surface. Its color ranges from colorless to yellow, brown, gray, orange, green, blue, white, black, purple, pink and (extremely rarely) red.
Q: How is a diamond certified?
A diamond is evaluated, measured, and scrutinized by trained individuals at the Gemological Institute of America (GIA) or the American Gem Society Laboratories (AGSL), using various industry tools. A certificate includes an analysis of the diamond’s clarity, color, dimensions, symmetry, polish and other characteristics. You should receive a certificate with any diamond you purchase. The GIA and AGSL laboratories are among the most respected in the diamond industry.
Q. Why do I need an independent diamond grading report?
For the ultimate peace of mind, ask your jeweler to provide an independent diamond grading report with your diamond. The most widely used and respected reports are those issued by the independent GIA Laboratory, which provides grading reports on the world’s most important diamonds. A professional jeweler can arrange to have your diamond graded and even have a personal message or unique GIA Diamond Grading Report number laser-inscribed onto the diamond’s girdle (its outer edge).
Q. Why get a diamond grading report or certificate from GIA?
Most consumer purchases of significant value come with important certified documentation. Houses have deeds. Vehicles have titles and registration, but what about something as important as a diamond? A Diamond Grading Report isn’t an appraisal but a scientific blueprint of your stone’s exact qualities. GIA’s heritage as a research and educational institution means they are trusted to provide accurate, unbiased diamond evaluations. All GIA diamond-grading reports contain a hologram, a security screen, and microprint lines as well as other security features that exceed industry guidelines. Simply put, they’re here to help you know what you’re buying. The most widely used and trusted means of verifying a diamond’s quality and provide positive identification is a Diamond Grading Report or Diamond Dossier®. A GIA grading report provides an expert analysis of a diamond’s quality based upon the “4Cs” of diamond grading: carat, color, cut and clarity. The GIA Diamond Grading Report also contains a plotting diagram that clearly shows the diamond’s unique inclusions and other clarity characteristics such as inclusions. It undergoes a technical screening process, determining its potential as a synthetic or diamond simulate and is tested to ensure that the color is natural. Because GIA is not affiliated with any commercial enterprise, impartial and accurate analysis of a diamond’s quality and value is assured. GIA employs hundreds of highly trained diamond graders, gemologists, research scientists who scrutinize the diamonds and analyze them, depending on size, with as many as 40 pairs of eyes for each stone. GIA Laboratory experts have graded some of the world’s most famous diamonds, including the legendary Hope Diamond (45.52 carats) and the De Beers Centenary Diamond (273.85 carats).
Q: What are the Four C’s?
Diamonds and other gemstones are weighed in metric carats: one carat is equal to 0.2 grams, about the same weight as a paperclip. (Don’t confuse carat with karat, as in “18K gold,” which refers to gold purity.) Just as a dollar is divided into 100 pennies, a carat is divided into 100 points. For example, a 50-point diamond weighs 0.50 carats. But two diamonds of equal weight can have very different values depending on the other members of the Four C’s: clarity, color and cut. The majority of diamonds used in fine jewelry weigh one carat or less. Because even a fraction of a carat can make a considerable difference in cost, precision is crucial. In the diamond industry, weight is often measured to the hundred thousandths of a carat, and rounded to a hundredth of a carat. Diamond weights greater than one carat are expressed in carats and decimals. (For instance, a 1.08 ct. stone would be described as “one point oh eight carats,” or “one oh eight.”)How did the carat system start? The carat, the standard unit of weight for diamonds and other gemstones, takes its name from the carob seed. Because these seeds had a fairly uniform weight, early gem traders used them as counterweights in their balance scales. The modern metric carat, equal to 0.2 grams, was adopted by the United States in 1913 and other countries soon after. Today, a carat weighs exactly the same in every corner of the world.
Diamond color is all about what you can’t see. Diamonds are valued by how closely they approach colorlessness – the less color, the higher their value. (The exception to this is fancy-color diamonds, such as pinks and blues, which lie outside this color range.) Most diamonds found in jewelry stores run from colorless to near-colorless, with slight hints of yellow or brown. GIA’s color-grading scale for diamonds is the industry standard. The scale begins with the letter D, representing colorless, and continues with increasing presence of color to the letter Z, or near-colorless. Each letter grade has a clearly defined range of color appearance. Diamonds are color-graded by comparing them to stones of known color under controlled lighting and precise viewing conditions. Many of these color distinctions are so subtle as to be invisible to the untrained eye. But these slight differences make a very big difference in diamond quality and price.
Because diamonds formed deep within the earth, under extreme heat and pressure, they often contain unique birthmarks, either internal (inclusions) or external (blemishes). Diamond clarity refers to the absence of these inclusions and blemishes. Diamonds without these birthmarks are rare, and rarity affects a diamond’s value. Using the GIA International Diamond Grading System™, diamonds are assigned a clarity grade that ranges from flawless (FL) to diamonds with obvious inclusions (I3). Every diamond is unique. None is absolutely perfect under 10× magnification, though some come close. Known as Flawless diamonds, these are exceptionally rare. Most jewelers have never even seen one.
The GIA Clarity Scale contains 11 grades, with most diamonds falling into the VS (very slightly included) or SI (slightly included) categories. In determining a clarity grade, the GIA system considers the size, nature, position, color or relief, and quantity of clarity characteristics visible under 10× magnification.
Flawless (FL) – No inclusions or blemishes are visible to a skilled grader using 10× magnification
Internally Flawless (IF) – No inclusions and only blemishes are visible to a skilled grader using 10× magnification
Very, Very Slightly Included (VVS1 and VVS2) – Inclusions are difficult for a skilled grader to see under 10× magnification
Very Slightly Included (VS1 and VS2) – Inclusions are clearly visible under 10× magnification but can be characterized as minor
Slightly Included (SI1 and SI2) – Inclusions are noticeable to a skilled grader using 10× magnification
Included (I1, I2, and I3) – Inclusions are obvious under 10× magnification and may affect transparency and brilliance
How did the GIA Clarity Scale come about?
Like the color scale, GIA’s clarity grading system developed because jewelers were using terms that were easily misinterpreted, such as “loupe clean,” or “piqué.” Today, even if you buy a diamond in another part of the world, the jeweler will likely use terms such as VVS1 or SI2, even if her language is French or Japanese instead of English.
Cut is the factor that fuels a diamond’s fire, sparkle and brilliance.
The traditional 58 facets in a round brilliant diamond, each precisely cut and defined, are as small as two millimeters in diameter. But without this precision, a diamond wouldn’t be nearly as beautiful. The allure of a particular diamond depends more on cut than anything else.
Though extremely difficult to analyze or quantify, the cut of any diamond has three attributes: brilliance (the total light reflected from a diamond), fire (the dispersion of light into the colors of the spectrum), and scintillation (the flashes of light, or sparkle, when a diamond is moved).
An understanding of diamond cut begins with the shape of a diamond. The standard round brilliant is the shape used in most diamond jewelry. All others are known as fancy shapes. Traditional fancy shapes include the marquise, pear, oval and emerald cuts. Hearts, cushions, triangles and a variety of others are also gaining popularity in diamond jewelry.
As a value factor, though, cut refers to a diamond’s proportions, symmetry and polish. For example, look at a side view of the standard round brilliant. The major components, from top to bottom, are the crown, girdle and pavilion. A round brilliant cut diamond has 57 or 58 facets, the 58th being a tiny flat facet at the bottom of the pavilion that’s known as the culet. The large, flat facet on the top is the table. The proportions of a diamond refer to the relationships between table size, crown angle and pavilion depth. A wide range of proportion combinations are possible, and these ultimately affect the stone’s interaction with light.
In early 2005, GIA unveiled a diamond cut grading system for standard round brilliants in the D-to-Z color range. This system, the product of more than 15 years of intensive research and testing, assigns an overall diamond cut grade ranging from Excellent to Poor.
How does pavilion depth affect a diamond’s cut?
The distance from the bottom of the girdle to the culet is the pavilion depth. A pavilion depth that’s too shallow or too deep will allow light to escape through the sides or the bottom of the stone. A well-cut diamond will direct more light through the crown.
Information from GIA.edu