Natural diamonds occur when carbon is exposed to extraordinary heat and pressure deep within the earth. This process can produce a variety of internal characteristics known as inclusions as well as external ones called blemishes. These distinguishing features make each diamond unique and are sometimes referred to as a stone's "birthmarks".
When a diamond is graded, the total amount of inclusions and blemishes directly impacts the stone's clarity and therefore its value. When a diamond contains no inclusions it is considered flawless. This type of diamond is very rare and extremely expensive. Most diamonds that are sold commercially today contain some inclusions. However the majority of them cannot be seen with the naked eye.
When an expert evaluates a diamond for clarity, the process involves determining the size, number, nature, relief, and position of these inclusions and blemishes. This person must also conclude how these characteristics affect the overall appearance of the particular diamond. The closer a diamond comes to being perfect (flawless), the higher its value. The examples below show how different grades of clarity would be marked during an evaluation.
The GIA Diamond Clarity Scale
The Gemological Institute of America International Diamond Grading System is the industry standard by which all diamonds are inspected for clarity and assigned a grade. In all probability, no matter where in the world you buy a diamond, sellers will use the GIA Clarity Scale to describe a stone's clarity.
This scale has six categories, some of which are divided. The total number of specific grades is 11. These clarity grades range from flawless (FL) to diamonds which contain obvious inclusions (I3). Most diamonds fall into the VS grade (very slightly included) or SI grade (slightly included).
The GIA Clarity Scale is as follows:
- Flawless (FL). No blemishes and no inclusions visible under 10x magnification.
- Internally Flawless (IF). No inclusions visible under 10x magnification.
- Very, Very Slightly Included (VVS1 and VVS2). Inclusions are so slight that even a skilled grader has difficulty seeing them using 10x magnification.
- Very Slightly Included (VS1 and VS2). Inclusions can be seen with a minimal amount of effort under 10x magnification but they are still characterized as minor.
- Slightly Included (SI1 and SI2). Inclusions are quite noticeable using 10x magnification.
- Included (I1, I2, and I3). Inclusions are very obvious under 10x magnification and may significantly affect brilliance and transparency.
Diamonds without blemishes and inclusions are extremely rare. A professional jeweler may never see even one over the course of a lifetime. Inclusions and blemishes are generally too small to be seen by anyone other than a trained expert. The average consumer may not be able to tell the difference between a VS1 and an SI2. While diamonds with these two differing grades of clarity may appear alike, the difference in quality and overall value can be quite significant. For this reason, an accurate assessment performed by a professional diamond grading expert is extremely important and highly recommended.