Cut

The cut of a diamond determines how a diamond shines; the cut does not refer to the shape of the diamond. The master diamond cutter has created the facets on the diamond to allow light to internally reflect from one mirror-like facet to another and disperse and reflect it through the top of the stone in a display of brilliance and fire. So when we talk about diamond cut we are referring to the reflective qualities of the diamond which determines its ability to handle light, which leads to brilliance. As shown in the images below, when a diamond is well-cut, light enters through the table (top of the stone) and travels to the pavilion where it reflects from one side to the other. If the diamond is cut poorly like in the diagrams below, where one is cut too deep and one too shallow, the light will escape from below. But when the cut is ideal, such as in the example on the right, the light reflects back out of the diamond through the table and to the observer's eye. This light is the brilliance we mentioned, and it's this flashing, fiery effect that makes diamonds so mesmerizing.

Colour

The colour grading for white diamonds starts from completely colourless, the most expensive to a faint yellow colour. The colour in a diamond is produced from chemical impurities contained in its composition. The whiter or colourless the diamond, the more brilliant it will be because it will allow more light to pass and be reflected back. Also the whiter the diamond, the more colours it will reflect back to achieve that desirable rainbow brilliance only a well-cut, colourless diamond can create.

The chart below shows the colour grading created by the Gemological Institute of America (GIA) which is the professional colour scale for white diamonds.

Diamond Colour D E F = Colourless
G H I J = Near Colourless
K L M = Very Faint Yellow
N O P Q R = Faint Yellow
S T U V W X Y Z = Light Yellow

Diamonds graded D - F are the rarest and most expensive, whereas the ones graded G - J are seemingly colourless to the untrained eye. The diamonds with grades K - Z are more noticeably yellower, however the choice always depends on the buyer's preference.

The colour grading for fancy coloured diamonds is very different from white diamonds, see other types of diamonds to learn more about coloured diamonds.

Clarity

A diamond's clarity is a measurement of the amount of blemishes (external flaws) or inclusions (internal flaws) a diamond contains. An inclusion can air bubbles, cracks, and non-diamond minerals found in the diamond.

The grading starts at F which is a completely flawless (internally & externally) and extremely rare diamond. The chart below is a GIA clarity scale showing the different grades of diamond clarity.

Diamond Clarity IF Internally flawless No internal flaws, but some surface flaws. Very rare.
VVS1- VVS2 Very Very Slightly Included Minute inclusions very difficult to detect under 10x magnification by a trained gemologist. VVS1 is slightly cleaner than VVS2.
VS1-VS2 Very Slightly Included Minor inclusions only visible under 10x magnification. VS1 is slightly cleaner than VS2.
SI1-SI2 Slightly Included Inclusions easy to see under 10x magnification but usually not visible with the naked eye. SI1 is slightly cleaner than SI2.
I1-I2-I3 Included Inclusions visible with the naked eye.

For grades F through SI, a diamond's clarity grade has an impact on the diamond's value, not on the unmagnified diamond's appearance.

GIA certificates include what is known as a "plot" of a diamond's inclusions -- think of it as a "diamond fingerprint." Since no two diamonds are exactly the same, comparing the uniqueness of your diamond's clarity characteristics with the plot provided on the diamond certificate offers assurance that the diamond you pay for is the same diamond you receive.

Carat

A carat is a unit of measurement for the weight of a diamond with one carat equaling to 200 milligrams, or 0.2 grams, also known as 100 points. Since larger diamonds are harder to find than smaller ones, the price of diamonds with respect to their carat weight goes up exponentially.

The image below shows an example of the change in carat weight with change in the diameter of a round diamond. But keep in mind that two diamonds of the same weight could have different sizes. Why? If a diamond is cut too shallow (or flat) it will have a larger diameter, but shallow depth and appear larger. Likewise, if a diamond is cut too deep (or pointed) it will have a smaller diameter and deep depth and appear smaller. This is why cut is so important.

What Diamond Size is the best?

    To choose the best carat weight of diamond, consider her style, the size of her finger, the size of your setting, and your budget.
  • If you have a set budget, explore all your options and you'll find that there is a wide range of diamond carat weights and qualities available in your price range.
  • If your recipient is very active or not used to wearing jewelry, she may find herself bumping or nicking her new ring. Consider a smaller size diamond or a setting that protects a larger diamond from getting knocked against doors and counters.
  • Also keep in mind that the smaller the finger, the larger the diamond will appear. A 1 1/2-carat diamond solitaire looks much larger on a size 4 finger than a size 8.
  • If you have already chosen a setting, make sure you choose a diamond to fit. Look for the diamond size specifications of your ring or ask your Blue Nile diamond and jewelry consultant what size diamond you should look for.
  • Finally, if a large carat weight is important to you, yet you're working within a budget, consider a diamond with a good cut, SI1-SI2 clarity, and an I or J color grade.

But the best way to determine what size is best is by getting an idea of what she is expecting. If you plan carefully, you can get some answers without even raising her suspicions.

Symbol Meaning Definition
F Flawless Free from all inclusions or blemishes.
IF Internally Flawless No inclusions visible at 10x magnification.
VVS1 Very Very Slightly Included #1 Inclusions that are extremely difficult to locate at 10x.
VVS2 Very Very Slightly Included #2 Inclusions that are very difficult to locate at 10x.
VS1 Very Slightly Included #1 Minor inclusions that are difficult to locate at 10x.
VS2 Very Slightly Included #2 Minor inclusions that are somewhat difficult to locate at 10x.
SI1 Slightly Included #1 Noticeable inclusions that are easy to locate at 10x.
Sl2 Slightly Included #2 Noticeable inclusion that are very easy to locate at 10x.
I1 Included #1 Obvious inclusions. Somewhat easy to locate with the unaided eye.
I2 Included #2 Obvious inclusions. Easy to locate with the unaided eye.
I3 Included #3 Obvious inclusions. Very easy to locate with the unaided eye

* The Above Chart Shows the Diamond Clarity Grading Guide.

GIA COLOR - COMMERCIAL GRADING
D
E
F
G
H
I
Colorless
(White)
J
K
L
Near Colorless
(White)
M Faint Yellow
N,O,P,Q,R Very Light Yellow
S,T,U,V,W,X,Y,Z Light Yellow

Without attention to quality cutting, light is lost and not returned to the eye.

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