The purer a diamond, the more brilliant. The greater a diamond's clarity, the more brilliant, valuable and rare it is - and more expensive. Virtually all natural diamonds contain identifying characteristics, yet many are invisible to the naked eye. These are nature's birthmarks, and may look like tiny crystals, clouds, or feathers. Diamonds categorized as internally flawless reveal no such inclusions.
Flawless stones are the most expensive and are treasured for their rarity and beauty.
Diamonds with very, very small inclusions are graded as VVS1 or VVS2. The larger the inclusion, the lower the grade and the less rare the diamond. Inclusions that can be seen with the naked eye are graded I1 to I3. The number, color, type, size and position of surface and internal birthmarks affect a diamond's value. Major inclusions can interfere with the path of light that travels through a diamond, diminishing its brilliance and sparkle and therefore its value.