Clarity Grades

A diamond's clarity refers to the presence of impurities on and within the stone. When diamonds form naturally under extreme heat and pressure, imperfections in the crystal structure can develop, and tiny traces of natural elements are almost always trapped inside. These internal characteristics are called inclusions.

Diamond clarity is one of the four primary characteristics used to evaluate a stone — the 4Cs. The diamond with the highest clarity grade is one with a complete absence of any detectable imperfection. Internal natural impurities are classified as inclusions, while surface blemishes are considered external flaws.

A diamond's shape can influence its apparent clarity. Some shapes tend to hide inclusions, while those with broader table facets are more prone to visible flaws. Classic round-cut and princess-cut diamonds conceal imperfections well, whereas step-cut shapes such as the emerald or Asscher have larger, more open tables that are less forgiving.

Types of Inclusions

Inclusions can occur in various forms within a diamond. Understanding the common types helps to appreciate what graders are looking for:

• —Cavity — An external hole in the surface that can appear anywhere on the stone and may affect durability depending on its position
• —Chip or feather — Surface imperfections sometimes left during the cutting process, typically found along the edge of the stone
• —Knot — Drag marks from the polishing process that break the surface so minutely that only magnification can identify them
• —Needle and pinpoint — Tiny imperfections shaped as their name suggests, visible only at very high magnification
• —Cloud — A cluster of microscopic inclusions within the diamond that appear as a haze; generally translucent and often do not affect the clarity grade
• —Twinning wisp — A structural imperfection where inclusions twist together, a flaw found primarily in fancy diamond shapes

The Clarity Scale

Experts developed a standardised clarity scale in the mid-twentieth century, which was refined into a more detailed grading system in the 1970s. The following grades represent the full clarity scale:

FL — Flawless

Completely flawless with no internal or external inclusions of any kind. These are the rarest diamonds — fewer than 0.1% of all gem-quality diamonds fall into this category. A Flawless diamond is an exquisite symbol of perfection.

IF — Internally Flawless

No inclusions, with only very minute surface blemishes — typically minor details of polish such as polish lines. These blemishes do not affect sparkle and can only be detected by a skilled grader under 10x magnification. Extremely rare and genuinely gorgeous.

VVS1 — Very Very Slightly Included 1

Contains very minute inclusions that are extremely small and often undetectable even by diamond professionals under 10x magnification. VVS1 offers excellent value compared to FL or IF while maintaining virtually the same visual appeal. The most common inclusions at this grade are pinpoints and naturals.

VVS2 — Very Very Slightly Included 2

Similar to VVS1 but with inclusions that are slightly more visible under magnification. This grade is considered the best value among the higher clarities and does not compromise the diamond's brilliance. Common VVS2 inclusions include clouds, pinpoints, feathers and naturals.

VS1 — Very Slightly Included 1

Contains very minor inclusions that can only be seen under magnification and have minimal impact on sparkle. VS is a very popular clarity range. Common VS1 inclusions include clouds, feathers, needles, crystals and indented naturals.

VS2 — Very Slightly Included 2

Similar to VS1 with inclusions that appear slightly larger under magnification. Not noticeable to the unaided eye and extremely popular for its value proposition. VS2 diamonds tend to have a few more inclusions than VS1 and the sizes are slightly larger, while still remaining microscopic.

SI1 — Slightly Included 1

Considered fine quality, with visible imperfections under 10x magnification. An SI1 diamond will sparkle brilliantly even with its minor inclusions, which may be invisible to the unaided eye. SI1 is extremely popular for its value. Common inclusions are larger crystals, twinning wisps, feathers, clouds and knots.

SI2 — Slightly Included 2

Possesses high sparkle with clarity inclusions that may be visible without magnification when examined closely. Most SI2 inclusions are undetectable to the unaided eye in normal viewing conditions. SI clarity grades offer excellent value.

I1 — Included

An I1 diamond will still shine brightly despite eye-visible inclusions. The imperfections can be seen without magnification when the diamond is closely examined, depending on their size and location. MOH London does not carry diamonds in the I2 or I3 range, as inclusions at those grades begin to noticeably detract from the stone's beauty.