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.
Ruby 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 ruby underwent no heat-treatment and is of natural origin. Silk is a preferred inclusions in rubies.
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 ruby, these inclusions look like human fingerprints
Color zoning - uneven color distribution in the ruby
Cavities - holes extending into the ruby from the surface
Chips - broken off pieces along the girdle or on the culet of the ruby
Ruby 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
Asian Gem Centre assigns the following clarity grades to its rubies:
A+: Perfection: The stone is clean to the eye, but not necessarily at 10x magnification.
A: Insignificant Inclusions: The stone has very small visible inclusions
B+: Very Slightly Included: Inclusions or small internal crystals are only slightly visible on close inspection
B: Slightly Included: Inclusions or small internal crystals are visible on close inspection.
C: Included: Inclusions are visible
Transparency
The degree of visibility through a ruby is known as its transparency. It is an often-overlooked characteristic when discussing rubies. Transparency is designated as follows:
Transparent - objects look clear and distinct through the stone. These rubies 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 ruby. 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
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 inclusion 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 fingerprint outlines
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
Asian Gem Centre assigns the following clarity grades to its sapphires:
Clarity Grades
Asian Gem Centre assigns the following clarity grades to its rubies:
A+: Perfection: The stone is clean to the eye, but not necessarily at 10x magnification.
A: Insignificant Inclusions: The stone has very small visible inclusions
B+: Very Slightly Included: Inclusions or small internal crystals are only slightly visible on close inspection
B: Slightly Included: Inclusions or small internal crystals are visible on close inspection.
Transparency
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 - no light passes through the stone
