C

Carat
Carat is one of the diamond grading 4Cs. The standard unit of measurement referring to the weight of a diamond. One carat is equivalent to 200 milligrams, or one-fifth of a gram.

Cavaity
A type of inclusion consisting of a large or deep opening in the diamond.

Certified diamond  
A diamond that has been sent to a independent diamond grading laboratory such as the GIA - Gemological Institute of America. Such a diamond will always be sold with its unique diamond grading report

Clarity
Refers to the incidence of inclusions (internal imperfections) and blemishes (external imperfections). Clarity is graded on a scale from Flawless (F) to Imperfect (I), and the size, number, position, nature and colour of these imperfections determine the clarity grade and greatly affect the value the diamond.

Claws
The metal that holds a diamond or gemstone in place. Also known as prongs.

Cleavage
The tendency of a crystalline mineral to break in certain definite directions called cleavage planes. A cleavage may be caused by inherent internal strain or by a sharp blow. The break may extend to the surface of a diamond.

Cloud
A group of minute white inclusions too small to be distinguishable from another that gives a cloudy or milky appearance inside the diamond.

Colour
Grading the colour of a diamond involves deciding how closely a diamond's colour appears to be colourlessness. The colour of a diamond is ranked on a scale from ‘D' to ‘Z', where ‘D' is colourless and ‘Z' has a noticeable tint of colour, typically yellow. Most diamonds have a trace of yellow or brown. With the exception of some natural fancy colours, such as blue, pink, purple, or red, the colourless grade is the most rare and hence the most valuable.

Crown
The upper part of the diamond just above the girdle. It consists of a large flat area on the top of the diamond known as the table, and several crown facets below it.

Crown angle
The angle measured between the girdle plane and the bezel facets. Along with the table size, the crown angle helps determine the amount of dispersion displayed by the diamond.

Crown height
The part of the diamond that is above the girdle.

Crystal
A type of inclusion. A crystal is a mineral deposit trapped inside the diamond, and can vary in colour.

Cutlet
The smallest facet at the bottom of a full-cut diamond, resembling a sharp point or tip at the bottom of the pavilion on a faceted diamond. When the culet is polished, it adds an extra facet to the diamond, i.e.: a normal round brilliant cut diamond has 57 facets if the culet is not polished and 58 facets if the culet is polished.

Cushion cut
A fancy shape diamond cut with rounded edges and sides, no sharp points. The shape of the cushion cut resembles a pillow or cushion, hence its name.

Cut
The cut of a diamond refers to the proportions given to the polished diamond by the diamond cutter. Proportions are the size and angle relationships between the facets and different parts of the diamond. Cut affects both the weight yield from a rough diamond and the optical efficiency of the polished diamond. It is the most important of the 4Cs in determining the diamond's overall fire, brilliance and scintillation.

 

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