Beyond the 4 C:s


To gain a more accurate value of diamonds, there are other factors to keep in mind in addition to the 4 C:s. These factors provide more detailed information about the diamond’s visual appearance and significantly affect the price. Remember that if two diamonds with the same parameters differ in price it is always for a reason. There is no such thing as a cheap, high quality diamond.

Ideal Cut

Round Brilliant Cut is the only diamond shape that comes with a Cut Grade on the diamond certificate. The cut determines the amount of light the diamond can refract to produce the desired sparkle.

Although Excellent is the highest and most sought-after cut grade, it is relatively easy to receive from a diamond grading perspective. The Excellent Cut grade features a relatively large span, making it easy to attain. This is why it’s imperative to buy a diamond that is not only grade Excellent in Cut but also within the Ideal range.

Even though Round diamonds is the only shape that comes with a Cut Grade on the certificate, fancy shapes does have ideal cuts to keep in mind when purchasing. Please read more about fancy shaped diamonds here


Symmetry describes the variations of the parameters that determine the diamond’s proportions. Such proportions can be lacking roundness, variation in crown heigh/pavilion depth, table is off-center or not parallel with the girdle, girdle thickness or misalignment.

Grading system:
Excellent – Very Good – Good – Fair – Poor


The polish describes and evaluates the presence of external characteristics of a polished diamond. These characteristics are caused during the manufacturing process or later through incorrect handling of the stones. These characteristics can be scratches, polishing lines, beard, burn marks and abraded facet edges.

Grading system:
Excellent – Very Good – Good – Fair – Poor


Fluorescence is the emission of visible light when an object (diamond) is exposed to ultraviolet light. 35% of all diamonds exhibit some degree of fluorescence.

There is no visible difference between a diamond featuring none – medium fluorescence in normal daylight. 

Fluorescence is harmless to the diamond but can affect the diamond’s luster if graded strong or very strong. However, lusterless and coarse diamonds are usually caused by other factors. (Read more under Luster)

A.P. Shaps offers clients the opportunity to view loose diamonds under UV-lamps and normal light if they desire to purchase a diamond with fluorescence.


Luster is not graded on the diamond certificate and can only be determined by a trained gemologist or diamond grader. Although Luster is not graded, it has a significant effect on the price. This is a common reason why a ‘perfect’ diamond (high in color and clarity) can be sold at a low price.

Luster is mainly caused by tiny, dotted inclusions or crystals (clouds) inside the diamond. Strong or very strong fluorescence can cause low luster in rare cases, giving the diamond a milky or hazy appearance. A diamond with excellent luster exhibits outstanding sparkle and brilliance.

BGM (Brown, Green, Milky)

BGM – brown, green and/or milky – is a well-known term in the diamond industry. Diamonds tend to come in brown and green tinges and hues. So, for example, when buying a lower-graded (in color) diamond, it doesn’t necessarily need to be yellowish. It might have a brown or green tint, making the diamond look dirty instead of warm as is the case with yellowish-colored diamonds.

Milky is a trade name for diamonds with low luster and a hazy appearance.

Therefore, you should always buy a diamond with no BGM.

Bowtie Effect

A diamond bow tie is a darkened area that runs across the diamond’s width. All elongated diamond shapes, such as the oval, radiant, pear and marquise, have some degree of a bow tie. The diamond bow tie is an imperfection formed when a diamond is cut and hence is a less desirable feature. Thus, when shopping for a diamond,  you may want to avoid large bow tie effects.

How much the bow tie affects your diamond depends on how well the diamond is cut. A well-cut diamond will show a minimal bow tie effect; however, there will always be some evidence of a bow tie effect.  In the end, you must decide how much of a bow-tie effect you’re willing to accept.

Ethical diamonds

Read about the Kimberley Process