Storefront on Jeweler's Row in Philadelphia

Monday, April 7, 2014

Continuing Education about Diamonds

As a professional gemologist, it is my duty to periodically brush up on my educational requirements regarding the items I sell.  Since our expertise here at the Sydney Rosen Company is primarily Diamonds, and April is the month of the Diamond, I felt it would be fun to go over some of the fundamentals with you all.

I'll start off with a diagram of the "modern" cut diamond.

There are 4 main parts of a full cut diamond.  The Crown, Pavilion, Girdle, and

.  The Crown is the top-half of the diamond from the Girdle to the Table.  The Pavilion is the bottom half of the diamond from the Girdle to the Culet.  The Girdle is the middle portion, which can range in thickness from thin to extremely thin, to thick to extremely thick, depending on how the diamond was cut.  The Culet is the point at the bottom of the diamond.  Older cut diamonds may have a large polished facet as a Culet instead of a point.  A fifth important part of a diamond is the Table, which is the large octagon shaped facet at the top of the stone.

Next I will briefly go over the 4 C's of Diamonds, which are Cut, Color, Clarity and Carat Weight.


A diamonds cut is determined as the combination of its relative proportions and how well they maximize the diamonds brilliance or light return.  Diamonds cut like the diagrams below will not display the proper amount sparkle.

The proper proportions and angles to create the most brilliant diamond are shown below:

In general, a diamonds brilliance is a factor of the Total Depth Percentage of a diamonds as compared to it's diameter, and the Diameter of the TABLE facet as compared to the Girdle Diameter which is shown below.
If the table size, and the total depth percentage fall within a desired range, the diamonds is said to be well cut.  The GIA goes further to give cut "grades" that range from Excellent, to Poor.  This cut grade system also takes into account Polish and  Symmetry, which are functions of how perfectly the rest of the diamond was finished.

Obviously, with the vast array of different diamond shapes, the desirable ranges for the table size and depth will vary from shape to shape.


Color is a much simpler metric.  It is the degree to which a diamond shows "color".  Diamonds are "Colorless" gems, however the vast majority are not perfectly white.  Most show some degree of yellow or sometimes brown.  The GIA developed a system that rates a diamonds color from D-Z.  D being the whitest, and Z the yellowest.  A Diamond's color is permanent, it is a function of trace elements that formed in the diamond as it was growing.  However, diamond can treated to improve it's Color.


Clarity is a measure of how free of inclusions or imperfection a diamond is.  Diamond is a mineral after all, and not all crystals will be perfect.  Most diamonds have blemishes and imperfections, however, if they cannot be seen to the naked to eye, they usually do not affect the overall beauty of the stone.

Carat Weight:

Carat weight is simple.  It is how much a diamond weighs on a gemological carat scale.  Carat weight and Cut have an interesting relationship, since how well a diamond is cut will determine how large it looks in comparison to it's true weight.

I hope this was a helpful reminder about the 4 C's.  There are more diagrams and more in depth lessons on our website.

Visit to learn more!