Diamond clarity (鑽石淨度) refers to the quality of a diamond that pertains to its internal visible appearance and detailed internal properties, most notably the presence and nature of visible internal inclusions, surface scratches, as well as flaws. Diamond clarity can be measured in carats. The higher the carat for a diamond, the more pure it is and thus the higher the clarity. However, it must also be kept in mind that just because a diamond clarity is high, this does not necessarily mean that a diamond is flawless. A diamond can have only minute internal or external inclusions or may even be flawless.
There are basically three levels on which to gauge a diamond’s clarity. Diamond clarity can be classified into first, second and third grade. The first two grades, first-class clarity, reflect inclusions or small superficial inclusions but do not affect the overall quality of the stone; while the second-class clarity has little or no external or internal inclusions but the stone has prominent internal inclusions which significantly affects the stone’s clarity.
Diamond clarity graded in the second level has a few visible inclusions but they are not of great value. On the other hand, diamonds with inclusions that are of greater in scale are graded as third grade. In addition to having visible inclusions, diamonds with significant internal and external blemishes are graded as fourth grade. The better the diamond clarity, the more rare it is. It is important that you consider the clarity of a diamond plot in determining the value of your ring.
The clarity grade have inclusions can be assessed using the latest laboratory techniques and methods as well as traditional methods such as the rocking test. The laboratory techniques that are used to assess diamond clarity grade are called the optical chromatic aberration (OCA) test and the refractive Index (RI) test. These two tests are based on the principle that an increase in the size of a flaw will result in an increase in the brilliance of the diamond. Other than the flaws, both OCA and RI tests can also identify inclusions such as inclusions of metal in the diamond structure. Diamonds with inclusions have lower carat weight but are of greater value because they are usually rarer than those without inclusions.
A significant aspect of assessing the clarity of a diamond is to check for inclusions. If you find inclusions in your diamond, then your diamond clarity grade will be less than perfect. However, just because your diamond clarity grade is low, it does not mean that your diamond is flawed. There could be other reasons why the diamond has fewer inclusions than other diamonds. For instance, some diamonds carry a surface coating or a surface treatment, which can affect the brilliance of the diamond. Hence, it is important to ask for a detailed report from your jeweler when you are buying loose diamonds.
The clarity grade “S” is used to assess the purity of the diamond. A diamond must pass the criterion set by the American Society of Appraisers (ASA) for being a good quality diamond. “S” grades are based on the number and type of visible inclusions present in the diamond. “S” grades are commonly used for commercial and insurance purposes.