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GIA Certification

GIA 4Cs Cut

Cut quality is the factor that fuels a diamond’s fire, sparkle and brilliance. The allure and beauty of a particular diamond depends more on cut quality than anything else.

The GIA Diamond Cut Grading System for standard round brilliants in the D-to-Z color range is based on the assessment of seven components. The first three — brightness (the total light reflected from a diamond), fire (the dispersion of light into the colors of the spectrum), and scintillation (the pattern of light and dark areas and the flashes of light, or sparkle, when a diamond is moved) — are appearance-based aspects. The remaining four — weight ratio, durability, polish, and symmetry — are related to a diamond's design and craftsmanship.

In GIA’s system, each component is assessed individually, taking into account the relative importance of that component in the overall cut quality of the diamond. Each cut grade, based on a relative scale from Excellent to Poor, represents a range of proportion sets and face-up appearances. There are many different proportion sets that produce attractive diamonds.

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. It is important to note that a wide range of proportion combinations are possible, and these ultimately affect the stone’s interaction with light and how attractive the diamond is to the person viewing it.

While it is important to consider many components when assessing the overall cut appearance and quality of round brilliant diamonds, an individual's preferences also play a role. Because each cut grade represents a wide range of proportion sets, individuals have the freedom to choose which particular appearance they prefer within the grade range.

The diamond industry as well as the public can use cut along with color, clarity, and carat weight to help them make more informed decisions when assessing and purchasing round brilliant diamonds.

CUT VS. SHAPE

People often use the words cut and shape interchangeably. They think of cut as the shape or outline of the diamond, rather than the arrangement of facets needed to create an attractive face-up appearance.

Round is the shape used in most diamond jewelry. All other outlines are known as fancy shapes. Examples of traditional fancy shapes include the marquise, pear and oval. Hearts, triangles and a variety of others are also gaining popularity in diamond jewelry.

GIA 4Cs Clarity

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 minor and range from difficult to somewhat easy for a skilled grader to see under 10x magnification

  • Slightly Included (SI1 and SI2) - Inclusions are noticeable to a skilled grader under 10x magnification

  • Included (I1, I2, and I3) - Inclusions are obvious under 10× magnification and may affect transparency and brilliance

GIA 4Cs Color

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 light yellow or brown. 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.

GIA 4Cs Carat Weight

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.”)

GIA Diamond Research

WHY IS DIAMOND THE ‘KING OF GEMS’?

From crowns to engagement rings, diamonds have been a central aspect of many of life’s celebrations and historical milestones. They have been associated with legends and folklore. Diamonds have set record per-carat prices and often reside at the pinnacle of the gem and jewelry world.

Diamond stands at the apex of the hardness scale with a value of 10. It also has the highest thermal conductivity and the highest molar density of any terrestrial material, as well as a high resistance to acids, corrosion, and radiation. This extraordinary combination of physical properties not only makes it ideal for daily wear in jewelry – often through many generations - but has also led to its exploitation for a wide range of industrial and technological applications. Diamond’s remarkable potential has spurred the rapid evolution of laboratory-grown gem-quality diamonds in the last 20 years.


NATURAL DIAMOND MINING

In addition to its value as a gemstone, diamond has enormous scientific value as a window into hidden processes occurring deep inside the earth. Given the sheer volume of diamonds passing through its laboratories, GIA is uniquely positioned to observe and learn from diamonds in way that no other research group can. Diamonds are the deepest derived material humans are able to observe at earth’s surface, with most forming at depths of 150–200 km. Analysis of inclusions in rare specimens has revealed that some large, top-quality gem diamonds belong to a special category called Superdeep Diamonds and come from even greater depths—as deep as 600 km or more. Diamonds have formed over a large proportion of geologic time, spanning back as far as 3.5 billion years, meaning these relatively small crystals contain an incredible record of the earth in both space and time.