Carat :
The unit of weight by which a diamond is measured. One carat equals 200 milligrams, or 0.2 grams. The word comes from the carob bean, whose consistent weight was used in times past to measure gemstones.
Carbon Spots :
An inaccurate term used by some people in the diamond industry to describe the appearance of certain inclusions in a diamond. The term refers to included crystals that have a dark appearance, rather than a white or transparent appearance, when viewed under a microscope. In most cases, these dark inclusions are not visible to the naked eye, and do not affect the brilliance of the diamond.
Cavity :
A type of inclusion consisting of a large or deep opening in the diamond. It may be cause by cleavage, by a blow, or may have been “pulled out” from the surface during the polishing operation.
Chip :
A curved break on a diamond that extends from a surface edge. (b) A small rose-cut diamond or single-cut melee. (c) A cleavage piece of diamond that weighs less than one carat. (d) A small, irregularly shaped diamond.
Cleavage :
The propensity of crystalline minerals, such as diamond, to split in one or more directions either along or parallel to certain planes, when struck by a blow. Cleavage is one of the two methods used by diamond cutters to split rough diamond crystals in preparation for the cutting process (sawing is the other method).
Clouds :
A grouping of a number of extremely tiny inclusions that are too small to be distinguishable from one another, even under magnification. The result is that, under a microscope, this grouping often looks like a soft transparent cloud inside the diamond. Of course, clouds cannot be seen with the naked eye. Usually, this sort of inclusion does not significantly impact a diamond's clarity grade.
Color Grading :
A system of grading diamond colors based on their colorlessness (for white diamonds) or their spectral hue, depth of color and purity of color (for fancy color diamonds). For white diamonds, use a grading system which runs from D (totally colorless) to Z (light yellow).
Crown :
The upper portion of a cut gemstone, which lies the girdle. The crown consists of a table facet surrounded by either star and bezel facets (on round diamonds and most fancy cuts) or concentric rows of facets reaching from the table to the girdle (on emerald cuts and other step cuts).
Crown Angle :
Crown Angle is 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 :
Crown Height is the millimeter distance the table is above the girdle.
Crown Height Percentage :
Crown Height Percentage is the crown height expressed as a percentage of the average girdle diameter.
Crystal :
Crystal is a type of inclusion where a mineral deposit is trapped inside the diamond.
Culet :
A tiny flat facet that diamond cutters sometimes add at the bottom of a diamond's pavilion. Its purpose is to protect the tip of the pavilion from being chipped or damaged. Once a diamond is set in jewelry, though, the setting itself generally provides the pavilion with sufficient protection from impact or wear. Most modern shapes have either no culet at all, or a small or very small culet.
Cut :
This refers both to the proportions and finish of a polished diamond. As one of "the Four Cs" of diamond value, it is the only man-made contribution to a diamond's beauty and value.
Cutting style :
Cutting styles are different than diamond shapes. The simplest and most common way to explain cutting style is to categorize it into the following three basic types: Step-cut, Brilliant-cut and Mixed-cut.
