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 Cs. These factors provide more detailed information about the diamond’s visual appearance and significantly affect the price.

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

The Sarine Instrument in the A.P. Shaps Diamond Laboratory measures all angles and proportions on the diamond. 


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

Polishing lines that’s caused during the polishing process of the diamond. Picture form GIA (Gemological Insititute of America)

Picture form GIA (Gemological Insititute of America)


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.

Our Promise

When buying a diamond from A.P. Shaps, our ultimate goal is to make it an intimate and special experience. The business model we visualize is simple: The customer’s individual needs and preferences always come first, and we strive to make your purchase a smooth and successful process. All our diamonds are genuine, untreated and conflict-free. If the diamond weighs 0.3 carats or more, it comes with a GIA (Gemological Institute of America) certificate certifying the diamond’s quality characteristics.If you have any concerns about your diamond choice, you are always welcome to contact us. Having quality services, high-quality products and satisfied customers are our highest priority.

Schedule an appointment in our showroom on Strandvägen 11 in Stockholm.