Below is a detailed explanation of the same.
Diamond Clarity Grades
The commonly used scale determined by the Gemological Institute of America has six grades. The FL stands for Flawless and represents the highest quality of
diamonds. The IF follows this, which stands for Internally
Flawless diamonds that have only a few surface blemishes on them. The next is the VVS or Very Very Slightly Included
clarity grade, which is followed by the
SI or Slightly Included.
The GIA scale divides the Slightly Included
diamonds further into SI1 and SI2. The truth is, SI3 grade does not exist in the GIA clarity scale but is employed by the European Gemological Laboratory to grade
gemstones of low
clarity.
The general confusion regarding SI3 was because it was being advertised as a subcategory under the SI range. In fact, many jewelers use the term SI3 to define a 7
ct diamond ring that cannot be included in SI1 but does not have the number of visible flaws as SI2 grade either. However, as the GIA does not grade such
stones, they will be of very value in the US.