What does "cat's eye" mean

Cat's Eye, a fascinating gemstone, is renowned for its distinctive optical phenomenon called the "chatoyancy"(For further reading please visit wikipedia)—a narrow, bright light band that resembles a cat's pupil.  

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Here’s a detailed introduction:  

1. 
   Geological Identity
     Mineral Species : The term "Cat's Eye" strictly refers to  chrysoberyl cat's eye , a rare variety of chrysoberyl (chemical formula: BeAl₂O₄).  
      Natural Origin : Formed in metamorphic rocks, often found in Sri Lanka, Brazil, and India. Other minerals with chatoyancy (e.g., quartz, tourmaline) are named after their base material (e.g., "quartz cat's eye"), but only chrysoberyl cat's eye is considered a premium gem.  
2. 
     Unique Optical Effect   
      Chatoyancy Mechanism : Caused by parallel inclusions (e.g., rutile needles) within the gemstone. When cut en cabochon (domed surface), these inclusions reflect light to create a moving, linear "eye" effect.  
      Light Behavior : The eye should be sharp, central, and unbroken, shifting as the gem is rotated. High quality cat's eyes exhibit a vivid, milky white band on a greenish yellow or brown base.  
3. 
     Physical Properties   
      Hardness : 8.5 on the Mohs scale, making it durable for jewelry.  
      Luster : Vitreous to oily luster, with the chatoyant band appearing metallic.  
      Color : Predominantly in shades of honey yellow, olive green, or brown. Rare blue or white varieties exist but are highly sought after.  
4. 
     Value and Rarity   
      Pricing Factors :  
        Eye Quality : A sharp, well defined, and centrally positioned eye commands the highest value.  
        Color : Rich, warm yellows (like "honey gold") are more valuable than pale tones.  
        Size : Gemstones over 5 carats are extremely rare; fine specimens can cost thousands of dollars per carat.  
      Collector’s Item : Sri Lankan cat's eyes are the most prized, often compared to "liquid gold" for their lustrous eye effect.  
5. 
     Uses and Care   
      Jewelry Applications : Commonly set in rings, pendants, or brooches as a centerpiece. Its unique effect makes it a statement gem in both classic and contemporary designs.  
      Maintenance : Avoid harsh chemicals and ultrasonic cleaners, as inclusions may be fragile. Clean with a soft cloth and mild soap.  
6. 
     Cultural Significance   
      Mythology : Believed to protect against evil in ancient Egyptian and Asian cultures. In India, it is associated with the planet Ketu and worn for spiritual guidance.  
      Modern Symbolism : Represented as a gem of intuition and clarity, often chosen by those seeking unique, meaningful jewelry.  
7. 
     Distinctions from Imitations   
      Common Fakes : Imitations include glass beads with painted lines, quartz cat's eye, or synthetic chrysoberyl.  
      Key Tests :  
        Hardness : Chrysoberyl cat's eye scratches quartz but not diamond.  
        Eye Movement : Natural cat's eyes have a fluid, three dimensional eye, unlike static imitations.  

For gem enthusiasts, Cat's Eye remains a testament to nature’s artistry, blending rarity, optical wonder, and timeless elegance.