Can someone help with explaining SI1, S12, I1-I3?

[BluePoppy]

Can someone explain why GIA grades some diamonds as SI1 or SI2, when inclusions are clearly visible to the naked eye? I thought if inclusions are easily visible to naked eye, viewing from top-down, 9-12 inches away - then the grade would be I1, I2, or I3.

 

[0-0-0]

https://4cs.gia.edu/en-us/diamond-clarity/

The GIA Diamond Clarity Scale is the global language for diamond clarity grading. Wherever you go in the world, whatever language is spoken, when buying a diamond, today you will likely hear terms like VVS1 or SI2 used to describe clarity.

Every diamond is evaluated under 10x magnification and assigned a clarity grade. A flawless diamond would receive an (FL) clarity grade; a diamond with obvious inclusions might receive a clarity grade of I3. Diamond clarity grades are based on the number, size, relief, nature, and location of characteristics. The clarity rating of a diamond is a reflection of the overall appearance of the stone – although many of these characteristics will likely not be visible to the naked eye.

Every diamond is truly unique, however most diamonds you see in jewelry stores fall between VS (very slightly included) and the SI (slightly included) on the clarity grading scale.

1 Universal System. 11 Grades.
All under 10x magnification

Flawless (FL) – No inclusions and no blemishes visible.

Internally Flawless (IF) – No inclusions visible but does have blemishes.

Very, Very Slightly Included (VVS1 and VVS2) – Inclusions so slight they are difficult for a skilled grader.

Very Slightly Included (VS1 and VS2) – Inclusions are observed with effort but can be characterized as minor.

Slightly Included (SI1 and SI2) – Inclusions are noticeable.

Included (I1, I2, and I3) – Inclusions are obvious which may affect transparency, brilliance and durability.

GIA clarity grading is based on how easy it is to spot inclusions under 10x. As for visibility to the naked eye, it all depends on the size/location/color of the actual inclusions. In some cases even VS2 clarity may not be eye clean if it has a sizeable dark crystal that is reflected across multiple facets. On the other hand, an I1 may be eye clean if it has clear inclusions that blends in with the faceting design.

 

[BluePoppy]

Ah, ok. Thank you for the explanation. I guess I thought that obvious inclusions with the naked eye would trump everything, automatically relegating it to I1, I2 or I3. Now I understand all the discussion about eye-clean.

 

[Texas Leaguer]

Just to add to what @0-0-0 explained, different shapes and sizes of diamonds may reveal inclusions to the naked eye more more easily in the same clarity grade. For example, a single crystal located beneath the table in a large stone may be eye visible even in a VS2 grade. And emerald cuts are notorious for revealing small inclusions to the naked eye.

But "eye-clean" is not really a grading criteria so if you are shopping for Si stones (and even some borderline VS2's) you need to know two things; First is your tolerance for being able to resolve an inclusion with your naked eye. And Second, if buying online, is to understand the merchant's definition of "eye-clean" since there is not a universal standard. And to note, some stones that are eye clean from the top are not eye-clean from the side, which is important info for may shoppers.

 

[BluePoppy]

Ahh... okay. More great information. Thank you. This information makes an experience that happened to be over 20 years ago make a lot more sense.... I was looking at a 2.5 carat emerald cut diamond. It was gorgeous, D/VS1. When I was looking at it from the top just with my own eyes, there was a tiny black dot on the table, near the corner. I remember asking the sales associate, and he looked at it with a loupe, and said "no that's not an inclusion. It's a reflection." But I was like, "It's a black dot visible without the loupe. I don't care if it's an inclusion or not, something is black in the corner."

 

[Texas Leaguer]

Ahh... okay. More great information. Thank you. This information makes an experience that happened to be over 20 years ago make a lot more sense.... I was looking at a 2.5 carat emerald cut diamond. It was gorgeous, D/VS1. When I was looking at it from the top just with my own eyes, there was a tiny black dot on the table, near the corner. I remember asking the sales associate, and he looked at it with a loupe, and said "no that's not an inclusion. It's a reflection." But I was like, "It's a black dot visible without the loupe. I don't care if it's an inclusion or not, something is black in the corner."

A accurately graded VS1, even in an emerald cut of that size, should be eye-clean. But if it was on the GIA stone plot, then you WERE seeing it with your naked eye. And if was a borderline VS2 then the probability of it being visible increases.

Another factor is individual visual acuity. For example, people that are near sighted are able to focus at a shorter distance and can often resolve inclusions that a person with "normal" vision cannot.

These are some of the variables that account for why laboratories do not make a direct "eye-clean" designation.