Diamond Inclusions

American Institute of Diamond Cutting, Inc.

Inside diamond inclusions

  This beautifully illustrated textbook was long overdue; an essential in depth study of diamond inclusions in all its known natural characteristics. The language throughout the book is simple and easy to understand. Both the novice and professional will find its information invaluable. The understanding of diamond inclusions is fundamental to grading finished diamonds as well as rough diamonds. This current work will allow the reader to become familiar with the variety of inclusions that exists in diamonds, what are their typical features, how to identify them and the impact they may have on the finished diamond.

This 208 page book addresses the subject of diamond inclusions by dividing it into four distinct areas.

A. External Characteristics, B. Internal Characteristics, C. Progression of inherent inclusions from rough to cut (Five rough diamonds documented), D. The diamond manufacturing process and its relationship to inclusions


           A. External Characteristics

             1. Features that are primarily natural in origin

             2. Features resulting from the manufacturing process

            3. Features resulting from wear and tear

             4. Features that are both external and internal


The natural seen in the pavilion of this diamond clearly displays the surface grain of the original rough crystal. (1.2)


Displayed on the pavilion point corners of this natural green blue emerald cut are two larger indented naturals. The right natural reveals obvious surface grain. (1.3)



           B. Internal Characteristics

             1. Features resulting from mineral type inclusions

(crystalline and solid) embedded in the body of the diamond

             2. Features resulting from impurities that existed within and around the formation of the crystal

             3. Features resulting from structural defects during and after the process of crystallization

             4. Features resulting from the manufacturing process and excessive wear and tear 




Examining the pavilion of this diamond from a side view, we can just discern a play of colors from reflected light within the included crystals.


This colorful photograph was captured when these included crystals were subjected to an intense light source, resulting in a strong play of bright colors. The included crystals were magnified at 70x. (9.4)



           C. The progression of inherent inclusions from rough to cut. (five rough diamonds documented)



Rotating the rough diamond to the opposite octahedral face, we can clearly observe the two feather inclusions that were visible on the left side of photo 14.1b. Both of the feather inclusions are surface reaching, but did not create any cavities on the surface. Additionally, we can detect two pinpoint carbon inclusions that are close to the surface. At the right bottom edge of the octahedral face are displayed bright prismatic colors, which strongly suggest tension in that area of the rough. Both the pinpoint carbon and the tension-filled area have a high probability of being removed in the manufacturing process. (14.3b)


At 22x magnification we can closely observe the tension-filled area that was seen in photo 14.3b. At the left and bottom we can inspect two well-shaped trigons.  (14.4b)



          D.The diamond manufacturing process and it relationship to inclusions



This feather inclusion ran parallel to the surface of the girdle. During bruting it cleaved, leaving a large cleavage break. Notice that part of the feather has penetrated under the surface of the girdle. (15.36)


b. Inclusions developing because of stress and strain

            As discussed previously, stress and strain in a diamond is very often unseen and is only realized when an inclusion develops for no apparent reason. If detected by using the polariscope, the bruter will use more caution during bruting but this is quite beyond his control if inclusions do develop.

            The forcing process that is used in bruting, if tension exist in one or more areas of the bruted surface, inclusions will suddenly develop due to the release of tension. The type of inclusions that develop are often feather type inclusions that trail from the bruted surface to varying depths internally. Sometimes as the brutting process continues, the inclusions can open or break away from the brutted surface creating pits, nicks and cavities.

c. Inclusions produced by the bruter

            During the bruting process, the bruter can sometimes press the industrial too hard against the gem diamond that is being brutted and thereby create a rough girdle. A rough girdle is where minute feather inclusions develop that extend from girdle surface to microscopic short distances.


The book "Diamond Inclusions" is a resource for the aspiring student, gemologist, diamond graders, diamond dealers, diamond cutters, and retail jeweler.