Planning to buy a diamond?
The most important criteria that a jeweler uses while grading a diamond are cut, clarity, color and carat weight. It is commonly known as the 4 Cs of a diamond. All four properties will determine how much a diamond is worth.
Most often a person gets confused and thinks cut is the shape of the diamond, but actually it refers to the angles and proportions of a diamond. Diamond cut is considered the most important of the four Cs, so it is important to understand how it affects the properties and values of a diamond. Diamonds that are cut either too deep or too shallow can lose or leak light through the sides and bottom and will be less brilliant-and ultimately of less value. But a well cut diamond is able to handle light better, creating more scintillation and more sparkle which leads to brilliance.
Diamonds are graded for clarity under 10x loupe magnification. Clarity ranges from flawless [perfect] to I [included]. Below is the chart that certification societies have standardized for grading to describe the clarity of a diamond.
F [flawless] : no internal or external flaws. Extremely rare.
IF [internally flawless] : no internal flaws, but may have minor flaws on the outside. Very rare.
VVS1 - VVS2 [very, very slight inclusions] : have very small inclusions. It's very difficult to detect inclusions under 10X magnification even by a trained gemologist. VVS1 inclusions can only be seen through the pavilion. VVS2 inclusions are more visible.
VS1-VS2 [very slightly included] : inclusions can only be seen with difficulty under 10x magnification. VS1 inclusions are harder to see than VS2.
SI1-SI2 [slightly included] : inclusions easy to see under 10x magnification and might be visible to the naked eye.
I1 - I2 - I3 [included] : inclusions visible to the human eye
Diamond color is usually referring to the presence or absence of color in white diamonds. Diamonds act as prisms and can divide light into a spectrum of colors and reflect this light as colorful flashes referred to as fire. The more colorless a diamond is the more colorful the fire will appear. Diamond colors generally range from D - Z for white and yellow diamonds. D is the whitest. Around S they become "Fancy" yellow Diamonds.
Carat - Weight
This is the weight of a diamond measured in carats. One carat is equivalent to 200 milligrams. Sometimes one carat is referred to as 100 "points", so that a diamond of 75 points weighs .75 carats. Carat-weight is the easiest of the 4Cs to determine. But two diamonds of equal weight can have very unequal value, depending on their cut, color and clarity. Larger diamonds often cost more per carat due to their size. Diamond cost increases exponentially with an increase in weight because larger diamonds are rarer than smaller diamonds and this rarity increases the value of a larger diamond.
But What About The 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.
[Gemological Institute of America]