Particularly in the case of colorless diamonds, clarity is one of the most important factors when assessing quality – and it is one of the four Cs. Perfect transparency is the best possible level of clarity, and this makes a jewel incredibly valuable because hardly any diamonds are completely free from inclusions and flaws, even though these may be microscopic. If a diamond is cloudy, light cannot penetrate the stone unimpeded. As a result, light beams are not optimally reflected by the facets and the jewel does not sparkle with full brilliance. Most flaws are very minor, however, and even experts cannot see them immediately with the naked eye. What is certain is that diamonds with high clarity are very rare, precious, and desirable.

Diamonds are pure carbon that has been crystallized under extreme conditions deep inside the earth over billions of years – a fascinating transformation. Before or during this process, foreign minerals may form and become embedded in the crystal, and these later impair the clarity of the diamond. The degree of clarity can still be reduced further after crystallization: high fluctuations in temperature and pressure or uneven cooling can cause stress fractures inside precious stones. As natural products, however, valuable jewels cannot be protected against such influences. Only in synthetic production can a diamond and its degree of clarity be specifically processed. This makes isolated finds of naturally occurring diamonds with perfect purity all the more exceptional.

When describing the clarity of a diamond, experts distinguish between internal and external flaws, depending on where these small aesthetic defects are found. Gray, black, or white spots inside the crystal are known as internal inclusions, whereas blemishes and other external flaws are on the surface. Typical, frequently occurring inclusions include pinpoints or needle-shaped crystals of various foreign minerals that were embedded inside the stone when it was formed. Sometimes several tiny crystals are very close together, similar to a cloud or mist, and this can cause milky opacity. There are also occasionally feathers – a term for microscopic fractures inside a diamond. These can reduce clarity, but larger feathers may also compromise the stability of a jewel. Lines, scratches, and abrasions on the surface of a gemstone are referred to as blemishes, and some of these are due to poor polishing or careless transport. As a rule, however, these inclusions are also very small and barely visible to the naked eye – if at all.

The International Clarity Scale was developed to standardize how diamond clarity is graded. Practically every gemstone is individually characterized by the natural circumstances of its origin, and no two are exactly alike. When assessing a diamond in terms of its clarity, experts consider the size, type, position, hue, and number of any internal or external inclusions at ten-times magnification. If no flaws can be identified even at this level, the jewel is classified as a flawless diamond with perfect clarity, and it is classified in the top category: “FL” (flawless). However, a diamond of imperfect clarity may still shine and sparkle with breathtaking beauty – the overall picture is what counts, not the number or size of defects. Most diamonds are “eye clean” and contain only inclusions that cannot be seen with the naked eye. Only diamonds with a lower level of clarity known as “Pique” have defects that are visible without a magnifying glass and that can actually reduce brilliance.