After color, the most important factor affecting the value of colored gemstones is clarity - a gemstone’s relative freedom from inclusions. Inclusions can affect both appearance and durability. The clarity grade is based on how visible inclusions are and how much they affect the appearance and durability of a gemstone.

Graders employ a system of five clarity grades ranging from eye clean down to severely included to classify clarity in transparent colored gemstones. The eye clean grade includes the top-clarity qualities of gems that commonly appear on the market. Colored stone graders do not use diamond grades to describe colored stones. Colored stones are rarely as clean as diamonds and should not be graded using the same criteria. Although some specimens do meet the standards of flawless clarity established for diamonds, the top qualities of most colored stones include gems with at least some inclusions. Blemishes are confined to the surface and are not considered as a part of clarity grading. Colored stones are clarity graded without magnification.

Multicolour.com uses two additional self-descriptive clarity grades which may be more appropriate for describing cabochons, phenomenal, and opaque stones.

1. Eye clean - appears clean to the unaided eye.
2. Slightly included - minor inclusions somewhat easy to see with the unaided eye.
3. Moderately included - Noticeable inclusions apparent to the unaided eye.
4. Heavily included - prominent inclusions that have a negative effect on either appearance, or durability.
5. Severely included - prominent inclusions that have a severe effect on appearance, durability, or both.
6. * Translucent
7. * Opaque

* Multicolour grades for cabs, phenomenal, and opaque stones.

Gem minerals form from several different geological processes. Gems produced by some of these processes tend to have more inclusions than those produced by other processes. For this reason, each gem species or variety has a range of clarity normally seen in the jewelry trade. Clarity ranges can be conveniently grouped into three Clarity Types. These apply only to transparent, non-phenomenal minerals (and color change minerals) that normally appear in the market as faceted gems.

Type 1: Stones that are often virtually inclusion free. They are so abundant in this quality that even minor inclusions detract from their desirability. Faceted Type 1 stones with eye-visible inclusions are rarely used in jewelry.

Type 2: Stones that are usually included. Stones with minor inclusions visible to the unaided eye are often faceted for use in jewelry.

Type 3: Stones that are almost always included. Even specimens with obvious inclusions are faceted for use in jewelry.

In this chart, species and groups appear in capital letters, varieties appear in upper and lower case letters.

When we judge the effects of inclusions and blemishes on clarity, we consider the following five factors:

• Nature

  Consider whether the inclusion is a type that threatens a gem’s durability. Some inclusions like feathers, are potentially damaging (this also depends on their size and position).

• Size

  Larger inclusions are usually more visible to the unaided eye and with certain types, more of a threat to durability. (Color, relief, and position also affect visibility.)

• Color and relief

  The more an inclusion differs in color or RI from the host material, the more obvious it is, due to higher relief.

• Number

  As inclusions become more numerous, they usually have a greater effect on appearance and durability. (depending on their size and visibility).

• Position

  The location of an inclusion often determines how visible it is or how much it affects durability.

• Cavity

  An opening or hole extending into the stone, usually angular in shape.

• Chip

  A damaged area near any edge of a stone, usually the girdle.

• Cloud

  Any hazy or milky area that cannot be described as a feather, fingerprint, or group of included crystals or needles.

• Color Zoning

  Areas or bands of concentrated or alternating colors.

• Feather

  A break in a stone, often with a white, feathery appearance.

• Fingerprint

  Inclusions in a pattern that resembles a human fingerprint.

• Growth zoning

  Visible internal evidence of the crystal growth process. Might be straight, irregular, or angular.

• Included crystal

  A mineral crystal trapped within a larger gem. Included crystals can be light or dark, transparent or opaque.

• Liquid inclusion

  A hollow or small pocket within a gem, filled with a liquid, and sometimes also a gas bubble and a solid crystal.

• Needle

  A long, thin inclusion.

• Silk

  Oriented, fine, needle-like inclusions that can create phenomena like cat´s eyes and stars.

1. Be sure of the stones identity and determine its clarity type.
2. Clean the stone thoroughly and carefully.
3. View the stone face up at a comfortable viewing distance with your unaided eye, under diffused light placed about 10 in. (25cm) above the stone.
4. Determine if there are any eye visible inclusions including unintended color zoning. If there are, determine how distracting they are.
5. Judge the effect of the inclusions (if any) on the clarity, based on the stones beauty and anticipated durability. You should consider nature, size, number, position, and relief.
6. If necessary, review the stone face up under 10X magnification to identify any inclusions that might affect durability.
7. Sum up the effects of the clarity characteristics as minute, minor, noticeable, obvious or prominent and indicate whether they have a negative or severely negative effect on appearance or durability.
8. Use these criteria for each clarity type to set the final clarity grade.

Although the GIA system defines and verbalizes clarity, the definitions for slightly and moderately included stones vary and are dependent upon of the clarity type of the gemstone being graded. Basically, a Type 1 gemstone like ZOISITE (tanzanite), that is normally free of any inclusions would be graded more severely than a Type 3 stone like an emerald which is almost always included. A slightly included tanzanite could only have minute inclusions difficult to see with the unaided eye while a slightly included emerald could have noticeable inclusions apparent to the unaided eye. Both stones are slightly included but the definitions vary and are more severe for type 1 gemstones.

Despite the descriptions, clarity grading is still subjective and interpretations will show some variations even among experienced graders. A brief description of the clarity grades follows.

Type 1 Clarity Grades	Type 2 Clarity Grades	Type 3 Clarity Grades
Eye clean – appears clean to the unaided eye.	Eye clean – appears clean to the unaided eye.	Eye clean – appears clean to the unaided eye.
Slightly included – minute inclusions difficult to see with the unaided eye.	Slightly included – minor inclusions easy to see with the unaided eye.	Slightly included – noticeable inclusions apparent to the unaided eye.
Moderately included - minor inclusions somewhat easy to see with the unaided eye.	Moderately included - noticeable inclusions apparent to the unaided eye.	Moderately included - obvious inclusions very apparent to the unaided eye.
Heavily included – prominent inclusions that have a negative effect on appearance or durability.	Heavily included – prominent inclusions that have a negative effect on appearance or durability.	Heavily included – prominent inclusions that have a negative effect on appearance or durability.
Severely included - prominent inclusions that have a severe effect on appearance or durability or both.	Severely included - prominent inclusions that have a severe effect on appearance or durability or both.	Severely included - prominent inclusions that have a severe effect on appearance or durability or both.