When shopping for a diamond engagement ring one should learn about “the four Cs” of diamonds, namely colour, cut, clarity, and carat. These determine the value and cost of a diamond.

Colour

When rating the colour of a diamond, jewellers commonly use the letters D through Z. The rating D represents a diamond that is colourless through to the rating Z has a yellow or brownish hue. As a rule, the closer a diamond is to colourless, the more valuable and beautiful it is.

Cut

Many people make the mistake of thinking that cut means the shape of the diamond. The cut actually refers to how many well-proportioned facets are in the stone. A well-cut diamond  regardless of its shape, sparkles and offers the greatest brilliance.

If a stone is cut poorly, it will appear less valuable because it will lack sparkle, brilliance and therefore, beauty. Some cutters will sacrifice cut to create the largest possible diamond, thus making too shallow or too deep of a cut and causing light to 'leak'out the sides and bottom of the diamond.

Cut is graded Ideal, Premium, Very Good, Good, Fair and Poor. Generally you should seek an Ideal to Very Good Diamond. If you're shopping with on a budget, opt for good.

Notice how the light is reflected withing the well cut diamond on top.

Clarity

Clarity is an indication of a diamond's purity. Diamonds frequently have inclusions, or small flaws, air bubbles, scratches, or other minerals inside the diamond. The less inclusions a diamond has, the more valuable and beautiful it is.

The scale for grading diamond's clarity is:

• Flawless-These diamonds do not have any inclusions and are considered to be perfect.
• Internally Flawless-These diamonds may have very minor blemishes on the outside of the stone.
• VVS1, VVS2-These diamonds have very, very small inclusions.
• VS1, VS2-These diamonds have very small inclusions.
• SI1, SI2, SI3-These diamonds have small inclusions.
• I1, I2, I3-These diamonds have flaws which can be seen with the human eye.

Carat

Carats refer to the size of the diamond. Each carat has one hundred points. The carat weight refers to the mass of a diamond.

For example, a diamond that is a 1/2 carat can also be referred to as a 50-point diamond. But bigger isn't necessarily better. A two-carat diamond that is cut poorly is not nearly as beautiful as a smaller diamond, cut by a skilled diamond artisan. Or, it may be cut well, but have poor colour and clarity.