The 4 Cs

Arthur Groom & Co. prides itself in its vast selection of diamonds and diamond jewelry. Buying a diamond from Arthur Groom & Co. is exciting and educational. Our experienced staff will guide you through the process of buying a diamond as they explain your choices and options using the 4 C’s of diamonds: Color, Clarity, Cut and Carat weight.


When referring to diamond color we refer to the presence or absence of color in diamond. Color is a result of the composition of the diamond, and it never changes over time. The formation process of a diamond ensures that only a few, rare diamonds are truly colorless. Thus the less color in a diamond the greater its value. To grade colorlessness we refer to GIA's professional color scale that begins with the highest rating of D for colorless, and travels down the alphabet to grade stones with traces of very faint or light yellowish or brownish color. The color scale continues all the way to Z. NOTE: Fancy color diamonds do not follow this rule. These diamonds, which are very rare and very expensive, can be any color from blue to green to bright yellow. They are actually more valuable for their color.


Clarity is the presence of identifying characteristics on (blemishes) and within (inclusions) a diamond. Diamonds are graded for clarity under 10x loupe magnification. Grades range from Flawless (diamonds which are completely free of blemishes and inclusions), to Included 3 (diamonds which possess large, heavy blemishes and inclusions that are visible to the naked eye). 

F | Flawless: No internal or external flaws.

IF | Internally Flawless: no internal flaws, but some surface flaws.

VVS1-VVS2 | Very Very Slightly Included (two grades). Minute inclusions very difficult to detect under 10 x magnifications by a trained gemologist.

VS1-VS2 | Very Slightly Included (two grades). Minute inclusions seen only with difficulty under 10x magnification.

SI1-SI2 | Slightly Included (two grades). Minute inclusions more easily detected under 10x magnification.

I1-I2-I3 | Included (three grades). Inclusions visible under 10x magnification and when viewed with the naked eye.


Diamond cut is perhaps the most important of the four Cs, so it is important to understand how this quality affects the properties and values of a diamond. A good cut gives a diamond its brilliance. The facets and finish of any diamond are what determine its ability to handle light, which leads to brilliance and fire.

Most gemologists agree that the best cut diamonds are those that follow a set formula calculated to maximize brilliance. These formulas can be seen in a diamond's proportions. If a diamond is well cut it will have maximum brilliance reflecting much of the light that enters it. If the cut is too shallow the light passes through the diamond and if it is cut too deep the light escapes through the diamond, both reflecting only a small proportion of the light that enters it.

Shape is often confused with cut. Shape is the outward appearance of the diamond, such as round, pear, marquise, etc.

Carat Weight

To determine carats, the diamond is weighed. One carat is equal to 100 points, so a ½ carat diamond weighs 50 points or 0.50 carats. Because large diamonds are more rare than small diamonds, the price of a diamond rises exponentially to its size.