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Diamond Plotting Diagram

What are the most common types of inclusions within a diamond?

Inclusions are the flaws or clarity characteristics found within a diamond. The clarity grade of a diamond is based upon a combination of factors, including the type of inclusion, size of the inclusion, location of the inclusion, and the overall quantity of inclusions.

It is said that the inclusions within every diamond are unique, in that no two diamonds contain inclusions in the exact same quantity, location, size, formation, etc.

The diamond industry uses plotting diagrams like the one pictured above, as a visual reference that is similar to a map, on diamond grading reports. The inclusions are indicated on the plotting diagram using different symbols for each type of inclusion, and listed beneath the plotting diagram in order of their prominence within the diamond. For instance, the order of the visibility of the inclusions within this diamond as seen using 10x magnification are cloud, crystals, and then the feather. It is not possible to determine whether a diamond is "eye clean" off of the plotting diagram alone.

Note that the Key to Symbols located beneath the plotting diagram references the type of inclusions present within the diamond, but refers to them in singular fashion even when more than one of that inclusion type is present within the diamond.

Types of Diamond Crystal Inclusions:

Diamond crystals are the most common type of inclusion found within gem quality diamonds, they are essentially tiny diamonds that were trapped within the larger diamond crystal as it formed. Diamond crystals can be translucent, white, or slightly dark in appearance, there is no way to determine the color or tonal value of an inclusion based on the plotting diagram alone.

Diamond crystals of any size and shape may be referred to as "crystal" on a diamond grading report, they may be circular or irregular in shape. Crystals are referenced on the plotting diagram by a solid red outline that roughly represents the outline of the diamond crystal.

Diamond crystals which are long and thin in shape, are commonly referred to as "needles" and most often look like a thin, white line when viewed under high magnification. They can be extremely difficult to locate using 10x magnification which is the standard for diamond clarity grading. Needle shaped diamond crystals are indicated on the plotting diagram as a straight, red line.

Extremely small diamond crystals which are the size of a pinpoint, are referred to as "pinpoints" and tend to look like sparkly specks of translucent dust when viewed under high magnification. Pinpoint size diamond crystals are indicated on the plotting diagram as single red dots.

When clustered together, groups of pinpoint size diamond crystals are known as "clouds" which are indicated on the plotting diagram by an outline comprised of tiny red dots.

It is common to see the comment "Pinpoints not shown" or "Clouds not shown" under the comments section of a diamond grading report, it merely indicates that additional clouds or pinpoints might be present within the diamond, but are not indicated on the plotting diagram. This is generally used when the inclusions are too slight to be found easily using 10x magnification, but they were noticed by the grader at higher levels of magnification which are beyond the industry standard of 10x.

What is a Feather within a Diamond?

A feather is a minute fracture within the crystal structure of a diamond that is usually of no consequence. It is called a "feather" because when viewed under high levels of magnification, they tend to look like a bird feather.

People tend to freak out when they hear the word fracture, but think of an ice cube, it is full of little cracks, air bubbles, and smaller pieces of ice which were trapped within the larger ice crystal as it formed. Yet the piece of ice is solid and structurally sound, the fact is that if a feather did not expand during the diamond cutting and polishing process, it is not likely to be an issue because the diamond was subjected to an extreme amount of pressure while it was being faceted.

What is a Natural and Indented Natural in a Diamond?

A "natural" is part of the original skin of a diamond which was left on during the cutting process, they usually appear along the girdle edge of a diamond and are of no consequence. The easiest way to think of a natural is that it is similar to the tree bark which might be found on a finished piece of wood, but it's extremely small and will be difficult for people to find without using extremely high levels of magnification.

An indented natural, is simply a natural which indents slightly into the surface of a diamond. Here again, indented naturals are usually located along the girdle edge of the diamond and will be difficult for people to locate and identify.

What is a Twinning Wisp within a Diamond?

A Twinning Wisp is intergrowth within the diamond, which is essentially just twisting of the crystal plane. Sometimes the twinning wisp formation will encompass other types of inclusions, such as diamond crystals, pinpoints, clouds, and feathers.

What is Internal and Surface Graining?

Under extremely high levels of magnification, diamond crystal looks like grain lines, and in some instances these grain lines will be visible to a trained grader. In those instances, the presence of internal or surface grain lines will be referenced on the diamond grading report. This is one of those inclusion types that you don't really need to give a second thought, it is not something which is easily detected even when using magnification.

What is a Cavity within a Diamond?

A cavity in a diamond is exactly what it sounds like, it consists of a small hole or gap within the crystal structure of the diamond. A cavity may be located entirely within the structure of a finished diamond, or it might appear, near or on the surface of the diamond.

What is a Chip on a Diamond?

A chip is also exactly what it sounds like, it is a small chip located on the surface of the diamond. In most instances, chips are extremely minute in size and are of no consequence.

What Inclusions Should I Avoid When Buying a Diamond?

In most instances, the inclusions within a diamond are extremely minute and are merely clarity characteristics which are used to determine the overall clarity grade of a diamond. The quantity and extent of the inclusions will be more prominent in lower clarity diamonds, such as those in the Included Level One (I-1) and Slightly Included Level Two (SI-2) clarity grades, where they are more apt to be noticeable without 10x and higher magnification.

The size and quantity of inclusions gets smaller as the clarity grade of the diamond increases, and they are apt to be less noticeable both with and without magnification.

So a feather in a VS-2 clarity diamond is going to be less of an issue than it might present in an SI-2 clarity diamond. Likewise, the visibility of diamond crystals in a VS-1 clarity diamond is going to be less noticeable than they would be in an SI-1 or SI-2 clarity diamond, it is all relative...

There really aren't inclusion types that I tend to avoid when buying diamonds, I consider them to simply be characteristics of the natural diamond crystal, which are going to be present within a diamond, just as there are impurities within an ice cube.

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