Clarity

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Blue sapphires tend to have more inclusions than most fancy-color sapphires. Gemologists use the term "inclusion" to define characteristics found inside a stone. Inclusions are often used as an indication that the gemstone is of natural origin. A "blemish" is a characteristic that affects the stone's surface. 

Sapphire Inclusions

• Crystals - solid inclusions of various shapes and sizes. Extremely small crystals are referred to as pinpoints or grains.
• Silk - fine fibers of titanium dioxide (rutile) or other minerals that resemble the look of silk. Well-formed silk indicates that the sapphire underwent no heat-treatment and is of natural origin. Silk is a preferred inclusions in sapphires.
• Needles - long, thin inclusions of either crystals, or tubes filled with gas or liquid (growth tubes)
• Cracks - feather-like inclusions also known as fractures or fissures
• Parting - breakage along a plane of weakness
• Twinning - two crystals grown out of one another or next to each other
• Halos - circular fractures surrounding a crystal
• Fingerprints - common in sapphire, these inclusions look like human fingerprints
• Color zoning - uneven color distribution in the sapphire
• Cavities - holes extending into the sapphire from the surface
• Chips - broken off pieces along the girdle or on the culet of the sapphire

Sapphire Surface Blemishes

• Scratches - lines scraped on a gemstone
• Pits - tiny holes on the stone's surface
• Nicks - broken parts of a stone's girdle or facet
• Abrasions - rough scrapings along the stone's facet edges

Clarity Grades

Gem Nation assigns the following clarity grades to its sapphires:

• VVS - Very, very slightly included - minor inclusions that can be seen under 10x magnification, but invisible to the naked eye. No effect on appearance.
• VS - Very slightly included - noticeable inclusions sometimes visible to the unaided eye, and very easy to see under 10x magnification. Little to no effect on brilliance.
• SI1 - Slightly included - large or numerous inclusions that can be easily seen under 10x magnification. These inclusions are apparent/very apparent with the naked eye. Slight effect on appearance, little to no effect on brilliance.
• SI2 - Slightly included - obvious inclusions that can be easily seen under 10x magnification. Slight effect on appearance and brilliance.
• I1 - Obvious inclusions - significant effect on appearance, brilliance and transparency
• I2 - Prominent inclusions - significant effect on appearance, brilliance and transparency
• I3 - Numerous and prominent inclusions - severe effect on appearance, brilliance and transparency

Transparency

Sapphire transparency ranging
from Transparent to Opaque.
Transparent is ideal.

The degree of visibility through a sapphire is known as its transparency. It is an often-overlooked characteristic when discussing sapphires. Transparency is designated as follows:

• Transparent - objects look clear and distinct through the stone. These sapphires usually have excellent brilliance despite any inclusions they may have.
• Semitransparent - objects look slightly hazy or blurry through the stone
• Translucent - objects are difficult to see through the sapphire. Light can pass through, but it is somewhat diffused.
• Semi-translucent or semi-opaque - a small fraction of light passes through the stone
• Opaque - almost no light passes through the stone