Clarity grades attempt to define the quantity, size, and position of inclusions in a diamond when examined under 10x magnification.
Below is the GIA clarity grading scale in descending order:
Flawless and internally flawless:
"Flawless" describes a diamond without any blemish or internal inclusion whatsoever.
"Internally Flawless" describes a diamond without internal inclusions but it might have a microscopic blemish on the surface that typically can be polished out. Both clarity grades are extremely rare.
VVS1 and VVS2 = very very slight inclusions:
VVS clarities describe inclusions barely visible even under 10x magnification . A typical VVS inclusion might be a single microscopic white pinpoint. The difference between VVS1 and VVS2 could be the position of the inclusion... Closer to the girdle [edge of the stone] = VVS1 whereas closer to the center = VVS2.
VS1 and VS2 = Very slight inclusions:
VS1 and VS2 inclusions are barely detectable under 10x magnification. While VS inclusions are slightly more prominent than VVS they remain insignificant. Once again the difference between VS1 and VS2 relates to the size, color, and location of the inclusions.
SI1 and SI2 = Slightly included:
SI1 and SI2 inclusions are easier to detect under 10x magnification but should not be visible to the naked eye. These clarities [selected with care] are a good choice for buyers who prefer a slightly larger diamond for their budget.
SI3 clarity: [Requires more explanation.]
The GIA grading system [established more than 50 years ago] does not recognize SI3 clarity. Diamond dealers however have been using SI3 to describe and price diamonds for decades.
Q: How did this happen?
A: Over time diamond merchants observed GIA "I1" clarity grades were covering too broad a range and felt the need for a grade between SI2 and I1. Gradually SI3 clarity and pricing worked its way into daily conversations between diamond merchants worldwide... until finally in 1989 SI3 became official, when the “Rappaport Diamond Report” included SI3 clarity on their weekly wholesale price list and it remains on the list to this day.
SI3 is now part of the fabric of the diamond business and selected carefully can provide excellent value.
Q: Why does the GIA not recognize SI3 clarity?
A: Their dilemma is how to handle the "millions" of existing GIA certificates with SI2 and I1 clarity grades? Each one would need to be re-examined and re-certified... a formidable task.
How to judge whether clarity is SI3 or I1?
If the inclusions do not affect brilliance and the diamond is definitely eye-clean... SI3 is appropriate. However if the diamond has visible inclusions... the appropriate clarity grade should be "I1".
Finally: I2 and I3 = Heavily Included:
These clarity grades have heavy inclusions clearly visible to the naked eye.
To get a complete understanding of clarity we recommend looking at different stones with the guidance of a skilled expert.