What is and how to identify Chatoyancy on a bead or cabochon.
Chatoyancy, also known as the cat’s eye effect, is an optical phenomenon where a bright, moving band of light appears on the surface of a gemstone, bead or cabochon, resembling a cat’s eye. To identify if a bead, gemstone or cabochon exhibit’s Chatoyancy, look for a single, narrow band of light that appears to move or shift across the surface when the bead or gemstone is rotated and with the cabochon shifted from sided to side or the light source is moved. This band of light is caused by the reflection off of parallel fibres or needle-like inclusions within the bead, gemstone or cabochon.
Here Is a more detailed breakdown:-
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Observe the light:- Hold the bead, gemstone or cabochon under a focus light source, such as a bright lamp or direct sunlight.
Rotate the bead/gemstone or turn the cabochon from side to side slowly under the direct light or move the light source.
Watch for bright, narrow band of light that appears to glow or move across the surface of the bead, gemstone or Cabochon.2. Identify the Cat’s-Eye effect:-
The band of light should be distinct and well defined not blurry or diffused.
The band of light should appear to move as you change the angle of the light or rotate the bead/gemstone or tilt the cabochon to a different angle.
The effect should be visible across the entire surface of the bead/gemstone or cabochon, not just in one spot.
3. Consider the cut:-
Chatoyancy is most visible in beads cut as cabochons, which have a smooth and rounded surface.
Beads with flat or faceted surfaces may not display the effect as prominently.
4.Look for fibrous Inclusions
While you may not see the inclusions themselves, their presence is what causes Chatoyancy.
The inclusions are typically parallel, creating the linar band of light.
5. Compare to known Examples;-
Familiarise yourself with the appearance of a Chatoyant gemstones like Tiger’s Eye, Cat’s Eye, Chrysoberyl.
This will help you recognise the effect when you see it in other beads, gemstones and cabochons.
6. Consider the materials
Certain materials are more prone to exhibiting Chatoyancy, such as those with fibrous or needle-like inclusions.
Examples include Tiger’s Eye, Cat’s Eye Chrysoberyl, and some types of quartz.
What doe Chatoyancy look like?
Gems exhibiting a single bright band are called Cat’s Eyes. This optical phenomenon called Chatoyancy is caused by light reflecting of parallel bundles of tiny hole tubes of fibrous crystals of another mineral inside the gemstone.
More about Chatoyancy
Chatoyancy also known as the Cat’s Eyes effect, is an optical phenomenon that appears as a bright, band of light moving across the surface of a gemstone or wood when it’s rotating or the light source is moved. This shimmering effect is caused by the reflection of light of parallel inclusions or grain patterns within the material.
Examples:-
Gemstones:-
The most well known example is Tiger’s Eye, a Chatoyant quartz variety. Other gemstones like Chrysoberyl, Tourmaline, and certain Sapphires can also exhibit this effect.
Wood:-
Certain types of wood, like quilted maple or some species of mahogany, can display Chatoyancy, often referred to as “figure” or “rope figure”.
Other Materials:-
Chatoyany can be found in other materials like certain types of abesto where parallel fibres are present.
Key Characteristics
Single Band of Light:-
Chatoyany is characterised by a single bright band of light, unlike asterism (star effect), which has multiple rays.
Movement:-
The band of light appears to move or glide across the surface as the light source or observer’s view point changes.
Cabochon Cut:-
Gemstones with Chatoyancy are often cut en cabochon (polished with a round top and a flat bottom) to maximise the visibility of the effect.
