When referring to diamonds, what exactly are the “4C’s”? Small or large, fine quality or not, these gems have very specific parameters of grading that can sometimes make the diamond worth the price of a car or the price of a house. These parameters, the 4C’s, can be highly technical and complicated.

The Four C’s are: Carat, Clarity, Color and Cut. Each are important and all need to be considered when evaluating a diamond for purchase. The Gemological Institute of America known as the GIA is a research and educational institution. GIA developed and continues to educate using a system and terminology for grading a diamond’s carat, clarity, color and cut.

Carat: refers to the weight of the diamond. The diameter as it refers to a round-cut does represent the weight but it is also tied greatly to its cut (which we will discuss later) The term carat, abbreviated as ct., originated from the word carob. Historically, the carob seed was used as a counter balance when measuring a stone’s weight. The carob seed was considered a uniform weight which made it easier to weigh gemstones in a fair way. A carat is divided by 100 parts referred to as points. A “twenty pointer”, 0.20 ct, is a 1/5 of a carat. A 1.50 ct. diamond can be referred to as one carat and fifty points.

Diamond carats

This diagram represents approximations based on diameters for a round brilliant-cut.

Clarity: is the term used to describe the internal characteristics of a stone, or how “clean” it is when viewed through 10X magnification. When there are internal characteristics, they are referred to as inclusions. This is a general term and can describe a range of things including an internal crystal or other features that form in a diamond crystal or while fashioning the diamond. These internal characteristics i.e. shape, size or placement are like a fingerprint, no two are alike. These identifying characteristics can be used to identify / recognize one diamond from another. Clarity grades range from Flawless to Imperfect. Imperfect (I clarity) is subdivided into categories represented by 1, 2 and 3 and determined by prominence of inclusions or blemishes, as well as its fragility. A flawless diamond is rare and the price will usually reflect this.

Diamond Clarity

This diagram shows GIA clarity grading nomenclature.


Color: refers to the absence or presence of color. Nature produces diamonds that most commonly occur in shades of yellow, brown or gray. Diamond color grading is done on a scale, like the clarity grades. A different type scale is used for fancy colored diamonds (i.e. red, blue, green etc.). The most expensive colorless diamond grade is D. As one descends from this colorless grade to diamonds with a slight color cast the letter grades go lower down the alphabet. A J or a K color has a detectable light color tinge. An O or P color has a noticeable body color.

Diamond Colors

This diagram shows a general representation of a range of colors.

Cut: refers to the proportions of the stone rather than the shape (i.e.; round, pear, marquise, princess, emerald etc.) of the stone. Cut is probably the most important factor and likely the most difficult to describe, but looking at two diamonds even an untrained eye would intuitively recognize the differences, possibly without knowing why. Cut refers to how a diamond interacts with light and the return of light to your eye which is called refraction. A poorly cut diamond will absorb light and appear dull. The exact proportions of a finely cut diamond will return a balance of white light and prismatic light which is called dispersion. Diamond cutters study diamond crystals intensely to determine its best light return. Each facet is a variable to a diamond’s cut, its shape and symmetry represents its relationship to each and every facet next to it. Where these facets meet is known as a facet junction and this too is a variable to the angle of each facet. Finally, the sharpness of the polish is another variable the optimizes a diamonds potential of maximum brilliance and dispersion.

Diamond Anatomy

This diagram features the anatomy of a diamond.


In conclusion, the 4C’s is a general overview of very complicated and specific variables that are taken into consideration in grading and ultimately valuing a diamond. For further in-depth detail of one or all of the 4C’s contact our gemologist at Clars Auction Gallery.