The 4Cs are the main parameters for valuating a diamond’s cost. They include weight in Carat, Color, Clarity and Cut.
Usually, an untrained person might be able to differentiate two of the four parameters: weight and color. The other two parameters, clarity and cut, are more complex and require expertise.
Most diamonds have natural internal characteristics named inclusions and external features named blemishes. These occur in the volcanic rock where the diamond is created. Clarity, therefore, refers to the nature, color, number and size of such inclusions or blemishes.
Examples of internal inclusions:
- Carbon: small black spots caused by carbon;
- Feathers: internal fractures that look like feathers;
- Clouds: minute microscopic crystals of dust-like appearance;
- Twinning plane: plane between two twin crystals created during growth;
- Needles: inclusions of the appearance of needles of Rutile compositions.
Examples of external inclusions:
- Chips: damage to the sharp edge of a facet;
- Bruising: mark caused by impact;
- Cavities: a dent caused either by a feather or the polishing process;
- Knots: a bulge caused by an inclusion penetrating the surface of a stone;
- Pits: minute pinpoint inclusions on the surface.
The GIA has established an internationally accepted grading system, according to which Clarity is graded from Flawless to Imperfect, as follows:
- FL (flawless): internal and external characteristics not visible to the naked eye. Such diamonds are rare and considerably more expensive than the lower-rated diamonds;
- IF (Internally Flawless): The same as FL, only IF exhibit insignificant minute external blemishes. Also these diamonds are rare and expensive;
- VVS1 (Very Very Small inclusions): inclusions extremely difficult to find under magnification;
- VVS2: inclusions quite difficult to find under magnification;
- VS1 (Very Small inclusions): minor inclusions difficult to see under magnification;
- VS2: minor inclusions somewhat easily found under magnification;
- SI1 (Small/Slight Inclusions): imperfections which might not be visible to the naked eye but under magnification inclusions are fairly easily detected;
- SI2: inclusions quite easily recognized under magnification;
- I1 (Imperfect): inclusions easily detected under magnification and visible to the naked eye when viewed through the top of the diamond;
- I2: inclusions easily seen with the naked eye;
- I3: evident and prominent inclusions and/or blemishes very easily detected with the naked eye.
Clarity grade is determined only when stones are viewed under a 10 power magnifying lens by an experienced grader. Grades FL trough SI, which are not visible when unmagnified, affect the value of the diamond but not its external appearance viewed with the naked eye.
Darker inclusions found in white or colorless diamonds will have the greatest affect on the drop of clarity grading of a diamond. Lighter inclusions in fancy colored diamonds are the cause of significant drop in clarity grade.
Containing several birthmarks or inclusions, the Excelsior is considered one on the world's most beautiful diamonds.
Read more about diamonds and about the 4Cs.