Diamonds are graded by the 4 “C’s”: clarity, color, cut and carat weight.
The GIA color scale and clarity scale have both allowed for a much greater amount of precision and consistency in grading diamonds. The GIA clarity scale is divided into five distinct groups: flawless/
internally flawless; very, very slightly included; very slightly included; slightly included; included. The word “included” refers to an inclusion, which is any material found inside a diamond (or any other gemstone). Inclusions will greatly lessen the value of a diamond; on the other hand, inclusions in star sapphires raise the value of those gemstones.
The GIA color scale uses letters of the alphabet, ranging from D to Z, to describe the range of color in diamonds. These letters are divided into five distinct groups: colorless (D-F); near colorless (G-J); faint (K-M); very light (N-R); and light (S-Z). Why start with the letter “D”? This was a conscious decision by the GIA to differentiate its grading system from older, more subjective grading scales that often used “A” or “AA” to describe colorless diamonds.
The quality of a diamond’s cut is more difficult to assess than its clarity or color. The GIA has five grades of diamond cut: excellent, very good, good, fair and poor. The cut of a diamond will affect its brightness (“Internal and external white light reflected from a diamond”), fire (“The scattering of white light into all the colors of the rainbow”) and scintillation (“The amount of sparkle a diamond produces, and the pattern of light and dark areas caused by reflections within the diamond”).
The last of the 4 “C’s” is carat weight. All things being equal, the value of a diamond increases dramatically with an increase in size, because large, clear diamonds are very rare indeed.
Most diamonds were formed over one billion years ago, at a depth of roughly one hundred miles below the surface of the earth, under tremendous pressures and at extremely high temperatures. Diamond is the gemstone of choice for the majority of engagement rings and wedding bands; it is the gemstone for the sixtieth and seventy-fifth wedding anniversaries, and it is the birthstone for April.
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