What is the highest grade a diamond can be?

Diamonds are graded according to cut, colour, clarity and carat weight. When cutting a rough diamond stone, the diamond cutter first determines the natural colour of the stone, then plans a cut that preserves the highest carat weight for its maximum clarity.

So the highest grade of diamond is the largest stone with zero flaws in the rarest colour with the most perfect cut for that stone. These diamonds are sold at auction and bring millions of dollars to sellers.

In jewelry, the D colour is the highest grade colour; internally flawless is the highest clarity, blue and red could be the rarest natural colours.

The Gemological Institute of America's Web site will help you better understand the four Cs, below.

Finally, exceptional stones, are also graded according to the type of diamond, the most common being Type I. Read more about diamond types, below.