Portland Diamond 4c's Guide

Diamond 4c's Guide - Cut

The Diamond's Cut 

Cut is a term which broadly refers to the shape of the diamond, and at a deeper level cut also refers to the geometry of the diamond, or the make. A diamond's only job is beauty, and the only thing it does to gain that quality is due to light optics, and the way the light travels in the stone. The combination of refraction and reflection produces an effect we call scintillation. 

Diamonds are cut into a number of shapes, depending on the nature of the rough stone. A cutter will decide based on the quality of the crystal what shape will yield the greatest value and prize. The most popular shapes are round, marquise, oval, pear, heart and emerald, and the choice is largely a matter of personal preference. There are also wonderous new shapes which are sheerly beautiful as well, the radiant cut and the princess cut come to mind instantly. Whatever the shape, however, a well cut diamond is the work of a master diamond cutter. When cut to good proportions, the diamond is better able to handle light, creating more scintillation, more sparkle. And that's a great reflection on you. 

How a diamond handles light: 

It is the cut that enables a diamond to make the best use of light. 

1. When a diamond is cut to good proportions, light is reflected from one facet to another and then dispersed through the top of the stone. This is a combination of reflection and refraction, where the light does not exceed the "critical angle", rebounds and exits via the crown. A very fine geometry also greatly increases the "masking effect" of activity within the diamond, and a lower clarity will appear much more "eye clean" due to the effect. My opinion is that the cut of a diamond is what drives the show, the geometry and the diamond's beauty are linked to the data and we can help you to get the best value and beauty. 

2. If the cut of the diamond is too deep, some light escapes though the opposite side of the pavilion. This is where the critical angle between reflection and the light passing out of the stone is exceeded, and the effect is called "Unplanned Light Loss." This effect can really dim the beauty of the diamond, so do be aware that a well cut diamond will give you a dazzeling effect like no other gem can. Poorly cut diamonds are discounted greatly for their lesser appeal. 

3. If the cut is to shallow, light escapes though the pavilion before it can be reflected. The AGS rates the ideal range for depth as between 58.5% up to 63%, and going below this in a round brilliant is not advised at all, the stone will become very dull and have the effect we call the "Fish Eye" effect. In essence, the light is lost out the back of the diamond, and remember a poorly cut diamond will easily be discounted 25% or more, so what seems a bargin can become an embarrasment.

Brilliant	Marquise	Pear
Emerald	Oval	Heart

One thing which bears mentioning is that different shapes will have radically different percentages and measurements. A princess cut might be 75% deep and have a 70% table and be a prime example of that shape. Trillions have a depth in the 30-40% range, and are picked for their brilliance and reflective qualities. We know that the world of diamonds can be a scary place for someone who wants to understand and we're here to help you do just that. We'll make the mysterious world of diamonds easy to understand, and we'll make finding that dream diamond a breeze. We're happy to help navigate with you... 

Diamond 4c's Guide - Color

The Diamond's Color

In most cases good color, is no apparant denegrating color.


Diamonds are found with a range of color, from faint yellow or brown through to the very rare pinks, blues, greens, and other colors known as "fancies". However, the best color of a diamond is no color, which is defined by a perfect "D" color. In practical terms the range for "Colorless" might best be defined as from "D" to "G" for Platinum, and where there is a yellow contrast in the ring, or colored gem, I think from "H" to "I" is a great range for eye popping white and bright. A totally colorless diamond allows light to pass effortlessly and be reflected and refracted into pinpoint rainbows of color. One might also offer that to give a woman such a diamond is to show your true colors as well. 

Diamond 4c's Guide - Clarity

The Diamond's Clarity 

Clarity is the measure of visible activity within the diamond. 

To determine a diamonds clarity, a diamond is viewed loose under 10-power magnification by a trained eye. Most diamonds contain very tiny natural "birth marks" which are known as inclusions. However, the fewer and smaller the inclusions are, the less likely it is that they will interfere with the passage of light though the diamond, and the more beautiful the diamond will be. The impact of clarity is different cuts will vastly vary. For example, where the perfect eye clean result might be achieved in a very finely cut round at "SI2" in an Emerald cut the degree of activity would kill the diamond as a choice, to all but Helen Keller. 

Remember that the masking effect of a very well cut diamond, and the brilliance that implies, will help carry what might otherwise be deemed a lower than desired grade. What I mean is that for a client seeking a very eye clean diamond an ideal cut "SI2" can be perfect for both savings and beauty. The clarity of a diamond will have a great impact on costs so geometry becomes a key factor for our choosing our diamonds, and should be for you choosing yours too. Most well cut brillianteered stones will be totally eye clean in the SI1 range and up, where step cut diamonds I highly recommend a clarity of VS1-2 or better for eye clean. 



Diamonds, more than any other gemstone, have the capability to produce the maximum amount of brilliance. A diamond that is free of both inclusions and surface blemishes is very rare and therefore more valuable. So, the clearer the diamond, the clearer your choice. 

While you'll need to vary clarity with different shapes and consider the efficiency of that cut in most cases for a round brilliant SI1 and up is totally perfect to the unaided eye, for step cuts I recommend a VS1 for a sense of perfection.

Diamond 4c's Guide - Carat

The Diamond's Carat 

The Measurement of weight of the diamond.

This is the weight of the diamond measured in carats. One carat is divided into 100 "points", so that a diamond of 75 points weights .75 carats. This ancient weight has been used for centuries for diamonds, and has become the universal standard. I like to say about now that gross weight is one of the major factors for anyone choosing a fine diamond, but also one should never forget the geomery of the cut, and the beauty a well cut diamond unlocks by nature. 

Carat-weight is the easiest of the 4 C's to determine. But two diamonds of equal weight can carry unequal value, depending on their cut, color and clarity. On the GIA certificates a notice informs that a poorly cut diamond can be discounted 25% or more, so be aware that weight is not the defining factor for picking your diamond.

Another thing to consider is that in a diamond which is cut too deep the diameter will be reduced. Many poorly cut diamonds are sold by others daily without explaining how attention to geometry in any given shape will always yield a better appearance and appeal