Gem Nation -- Cut -- Girdle Thickness

 

	The girdle divides the crown and the pavilion and serves an important role in protecting the edge of the stone from damage. The girdle should be thin enough so that it appears as a light line. Thick girdles reduce the amount of light returned to the eye by refracting light away from the observer. This effect, in turn, reduces the brilliance of the diamond. The more even the girdle, the better. If a girdle is too thin (extremely thin), it may easily fracture either during setting or through normal wear. The bottom line: Look for a girdle that is either: Very Thin to Thin, Thin to Medium, or Medium to Slightly Thick. Polished or faceted girdles are preferred for their improved optical effects.
			Extremely Thin Also called a "knife-edge", this type of girdle should be avoided. Unless the diamond setter or the wearer is extremely careful, a diamond with an extremely thin girdle is prone to easy fracture. An extremely thin girdle will be about 0.5% - 1% of the girdle diameter in a 1ct diamond.
			Very Thin A very thin girdle is considered by many to be an ideal girdle thickness. It will range from about 1% - 1.5% of the girdle diameter in a 1ct diamond.
			Thin An excellent choice in a diamond, a thin girdle will protect the stone and ensure that the minimum of light is lost through refraction. It will be around 2% of the girdle diameter in a 1ct diamond.
			Medium A medium girdle will be around 3% of the girdle diameter in a 1ct diamond. A very good choice in a diamond.
			Slightly Thick A slightly thick girdle will be around 3.5% of the girdle diameter in a 1ct diamond. Medium to slightly thick and slightly thick to thick are acceptable girdle choices.
			Thick Thick girdles permit loss of light through refraction. In a 1ct diamond, a thick girdle may be 4% of the girdle diameter.
			Very Thick A very thick girdle is undesirable to the overall "make" of a diamond. In addition to adversely affecting the color of the diamond, it also permits a considerable loss of light. A very thick girdle may be up to 5% of the diamond's girdle diameter.
			Extremely Thick An extremely thick girdle will exceed 5% of the girdle diameter. Not only will a consdirable amount of light be lost through the girdle, but the color of the diamond will be negatively impacted.