Diamonds Education & Grading System

Because diamonds are so valuable, it’s essential to have a universal grading system for comparing their quality.  When you are planning on purchasing a diamond it is important that you know as much as possible about how diamonds are classified.

Invented by De Beers in 1939, the standards largely adopted by the diamond industry are known as the 4Cs: Cut, Clarity, Colour and Carat.

In the 1940’s and 1950’s the Gemological Institute of America developed the 4C’s and the GIA International Diamond Grading System to objectively compare and evaluate diamonds.

For a more in depth education on the 4 C’s please see the link above to the Gemological Institute of America’s website.


When you think of the cut, you probably think of the shape of the diamond. You are partially correct. While cut does refer to shape, it also refers to the proportions of how the diamond is actually cut.

Diamonds are cut into many different shapes, reflecting not only popular taste but the proportions and quality of the rough diamond. The most popular shapes include Round, Oval, Square, Princess, Emerald, Baquette, and Marquise cuts. Many specialty shapes are also available.

A diamond’s overall proportions, as well as the size and placement of its many reflective surfaces or facets, also play a large part in “cut.” The consistency and balance of these can greatly affect how the stone captures light and reflects it back to the eye.


With the exception of some fancy colored diamonds, the most valuable diamonds are those with the least color. The color scale for transparent diamonds runs from D-F (colorless), G-J (near colorless), K-L (faint yellow), to Z (light yellow). Completely colorless diamonds are rare.

When diamonds are formed with traces of other minerals, rare and beautiful colors can result. These “fancy” colors range from blue to brilliant yellow to red, brown, pale green, pink, and violet. Because of their rarity, colored diamonds are highly desirable and may be quite valuable.


A diamond’s clarity is measured by the existence, or absence, of visible flaws. Tiny surface blemishes or internal inclusions — even those seen only under magnification with a jeweler’s loupe — can alter the brilliance of the diamond and, thus, effect its value. Clarity levels begin with Flawless (F & IF) and move down to Very Very Slight (VVS1 & 2), Very Slight (VS1 & 2), Slightly Included (SI1 & 2), and Included (I1, 2 & 3).

FL, IF DiamondsFlawless: No internal or external flaws Internally Flawless: No internal flaws
VVS1, VVS2 DiamondsVery, Very Slightly Included: Very difficult to see inclusions under 10% magnification.
VS1, VS2 DiamondsVery Slightly included: Inclusions are not typically visible to the unaided eye,
SI1, SI2 DiamondsSlightly included: Inclusions are visible under 10× magnification and may be visible to the unaided eye.
I1, I2, I3 DiamondsIncluded: Inclusions are visible with the unaided eye.

Carat Weight

The size of a diamond is measured, not by its dimensions, but by weight. One carat, the traditional unit of measure for diamonds, is equal to approximately 0.2 grams. You may also hear the weight of a diamond referred to in points. A point is equal to 1/100 of a carat; therefore, a 75-point diamond equals 0.75 carat. Diamonds of equal weight may appear slightly different in size, depending on their depth and proportions. Because they are quite rare, larger diamonds of gem quality are much more valuable.

A diamond’s weight is measured in what is known as a “Carat”, which is a small unit of measurement equal to 200 milligrams. Carat weight is commonly expressed in points or fractions. There are 100 points per 1 carat. For example, 0.33 carats is usually expressed as 33 points, or 1/3 of a carat. The charts below show the relative size of carat weights for different diamond shapes.

What does total carat weight mean?

The diamond’s total carat weight is a combined minimum carat weight of all the diamonds in a piece of jewelry. An example is if a pair of diamond stud earrings has a total diamond carat weight of ½ (.50) carat, each earring in this pair would have an individual carat weight of ¼ (.25) carat.

However, the actual diamond you purchase may weigh slightly more or less than the fractional weight specified. Because of this, the Federal Trade Commission has strict guidelines about the range of carat weight that a fraction can represent. The chart below shows the satisfactory ranges for carat weights expressed as fractions.

  • 1/4 carat total weight may be 0.21 to 0.29 carats
  • 1/3 carat total weight may be 0.30 to 0.36 carats
  • 1/2 carat total weight may be 0.45 to 0.59 carats
  • 3/4 carat total weight may be 0.70 to 0.84 carats
  • 1 carat total weight may be 0.95 to 1.10 carats
  • 1 1/4 carats total weight may be 1.20 to 1.29 carats
  • 1 1/2 carats total weight may be 1.45 to 1.55 carats
  • 2 carats total weight may be 1.95 to 2.05 carats

Why is carat weight important?

The carat weight of a diamond is one of the major factors affecting its price, along with cut, clarity and colour. Larger diamonds are rarer than small ones, so its value increases exponentially for higher carat weights.

How does carat weight affect diamond size?

As diamond carat size increases, the diameter and the depth of the diamond will also increase. This is the reason a 1 carat diamond approximately 6.5mm in diameter will not look twice as wide as a 1/2 carat diamond that is approximately 5mm in diameter.


Every diamond will have a distinct set of properties and proportions that define its anatomy.
The below guide will help you identify these areas:

Crown: The top part of a diamond extending from the table to the girdle.

Culet: The small or pointed facet at the very bottom of a polished stone.

Depth: The total height of a diamond as measured from the table to the culet.

Diameter: Width of a polished stone that is measured from edge to edge.

Girdle: The very edge of the diamond where the crown and pavilion meet.

Pavilion: The underside of a diamond extending from the girdle down to the culet.

Table: Largest polished facet located on the top portion of the diamond.


The shape of a diamond describes its appearance when viewed from above. Through different cutting processes a diamond takes a variety of shapes. While all diamond shapes have special attributes, the overall choice will depend on your personal preference. Popular Stone Shapes:

Asscher Cut

This shape has a pavilion that is cut with rectangular facets in the same style as the emerald-cut. However, it has cropped corners giving it a square appearance. This square emerald diamond is made with the step-cut process. It is bright, shiny and clear. This stone shape is best when set with a prong setting such as a four prong or six prong style.

Brilliant Cut / Round

The most popular diamond shape is currently the round-brilliant cut. This diamond cut is optically brilliant diamond because of its 360-degree symmetrical shape. For a large amount of sparkle and a classic shape, the round-brilliant is a great choice. This stone shape also works well with nearly all mounting types including four prong, six prong, channel, bezel, half-bezel and illusion.


Also known as “pillow cut” diamonds, the cushion is an antique cut that has both a classic and romantic appeal. The Cushion-Cut diamond has 58 larger facets and rounded corners which increase its brilliance. There are square and rectangular variations of cushion cuts.


The classic cut emerald has a unique pavilion that is cut with rectangular facets to create a distinctive optical appearance. Due to its larger, open table, this diamond shape showcases the clarity of a diamond the best. The blocked corners are usually cut to a rectangular outline, but can be cut in a square shape. Since they can vary greatly in how rectangular they are and your preference is for an emerald cut with a squared outline, look instead at the Asscher-cut diamond.

Half Moon

There are two varieties – step cut half-moons and (the more common) brilliant cut half moons. Half moons can be proportioned differently – chubby ones being less elegant and desirable than the slim elongated type.


The ultimate expression of romance and love, the heart shaped diamond is cut with triangular and kite-shaped facets which reflect light. Generally there are 59 facets on a heart shaped diamond. The cut is similar to a pear shaped diamond, except the cleft at the top of the heart shaped diamond is strategically cut to remove inclusions without affecting the total diamond weight.


The marquise cut is another brilliant-cut diamonds whose elongated shape can maximize the carat weight, giving you a larger carat weight per stone. Featuring narrowing points at both ends of the diamonds, this shape tends to flatter the finger well because it makes it appear longer. This shape works great in a solitaire setting or when paired with beautiful side stones.


The oval cut has beautiful brilliance very similar to a round-brilliant cut. An oval shape combines the sparkle of the round shapes with a finger flattering, elongated outline. It makes a good choice for someone who wants something more unique but still wants the fire and brilliance of a round cut diamond. The relatively symmetrical shape lends itself well to a variety of mounting styles. Most oval cuts work in a mounting with six prongs properly spaced for security.


The less common but visually interesting pear shaped diamond is a unique variation of the round diamond cut. There are generally 58 facets which allow the light to pass through it just as well as the round diamond cut. It is a popular choice for many solitaire diamond engagement rings or diamond rings with side stones.


The princess cut is the 2nd most popular diamond shape because of its modern classic shape offering clean lines and immense sparkle. A princess cut has either a square rectangular appearance depending on the way it was cut. The cutting process utilizes the step-cutting of the emerald cut with the triangular facets of the brilliant cut. Princess cuts will work best in a prong or channel setting.


The distinctive trimmed corners give a radiant cut its beautiful appeal. This diamond shape combines a square or rectangular shape with the brilliance of the traditional round cut. It combines the Round Cut style and the Emerald Cut style to make a non-traditional diamond. A radiant cut looks great in a solitaire setting or when prong set with side stones.


Shields are beautiful whether they are step or brilliant cut. They are great transitional stones that could be paired with virtually any center stone. The most elegant ratio is 1:1 but even elongated they are elegant, complimentary, and appropriate companions to the center stone.

Square Cushion

This diamond shape combines a square cut with rounded corners, much like a pillow (hence the name). This classic cut has been around for almost 200 years, and for the first century of its existence was the most popular diamond shape (similar to round cut today).

Square Radiant

The radiant cut diamond is the first square cut to have a complete brilliant-cut facet pattern applied to both the crown and pavilion, creating a vibrant and lively square diamond. The cropped corner square shape of the radiant is a nice bridge between a cushion and a princess cut, and for that reason looks beautiful set with both rounded and square cornered diamonds.

Straight Baguette

Elongated rectangular step cuts could be set either north-south or east-west. When set north-south they are commonly staggered on top of each other forming a ladder-like element. This is the only way they could appear in a modern ring. Set any other way they would contribute to creating an Art Deco look.

Tapered Baguette

These are the most common side stones used in engagement rings. Some might argue that a ring with tapered baguettes should not be called a three stone ring; it should be called a solitaire.  This is because baguettes are really not an extension of the center stone. They are set on the “cathedral’ part of the shank.


Trapezoid diamonds are tapered on both ends to form a trapeze. This perspective view of straight baguettes allows for a graceful transition from a large center stone to a narrow shank of the ring. They work great with other step cut stones such as an emerald cut or Asscher cut. They are also a nice fit as part of a traps/bullet combination, which is popular in five stone rings.


Triangular Brilliants, also known as Trillions and Trilliants, are mixed cuts with three equally straight or slightly curved sides. They are typically shallow and often seen as side stones for other fancy shapes, but when well proportioned, one can also be a stunning centerpiece in an engagement ring.



A Diamond Certificate or Diamond Grading Report is a statement, issued by an independent Gemological Laboratory, that at the time of evaluation, the diamond in question has been examined, measured, and scrutinized by experienced Diamond Graders, using various gemological instruments, and determined to contain the characteristics as stated in the Certificate or Report.

In other words, a diamond certificate can be accurately described as the blueprint of a diamond. This Certificate or Report includes an analysis of the diamond’s characteristics in an easy to understand format. Generally a certificate or report covers following characteristics of a diamond along with the laboratory and certificate details:

  • Name of the Laboratory
  • Certificate Number
  • Shape and Cutting Style
  • Measurements of the Diamond’s diameter
  • Carat Weight
  • Color Grade
  • Clarity Grade
  • Cut Grade
  • Finish, Polish & Symmetry
  • Fluorescence
  • Comments
  • Plotted diagram of the diamond for the imperfections.
  • Key to Symbols that helps us to identify characteristics marked in the plot.
  • Security Features for the Certificate
  • Graphical image of Diamond Structure
  • Information about Diamond’s Depth, Table, Girdles, Culet and Facets etc.

This certificate doesn’t state monetary value of a diamond.

There are many laboratories available throughout the world for diamond certification but below mentioned laboratories are considered as most respected ones in the industry, for their consistency and unbiased diamond grading systems.

The Gemological Institute of America (GIA), the American Gem Society Laboratories (AGS), IGI – International Gemological Institute and EGL – European Gemological Laboratories.



Diamonds are remarkably durable, resistant to scratching except by another diamond, and maintain their brilliant fire extremely well. These qualities make a diamond well-suited to regular wear and are perfect for engagement and wedding rings, which are usually worn every day.

But even a diamond isn’t indestructible. It can be chipped by a sharp blow or become loose in its setting and fall out. A diamond should be worn with care.

Because diamonds tend to pick up grease and oils, they can become dirty with handling and should be occasionally wiped with a lint-free cloth. Other methods for safe cleaning include warm water, mild soap, and a soft toothbrush or a commercial cleaning solution. It is not recommended to use ultrasonic and steam cleaners