According to Indian astrology, you must wear Cat's Eye on the advice of a qualified astrologer who can ascertain Ketu's position in your horoscope. It is not zodiac specific. Also, this gemstone is meant for specific troubled periods and many times not forever.

Weight: Typically, the gemstone size should be approximately 1/10th of your body weight, which means 1 carat for every 10 kgs. Alternatively, it can be according to the strength required as per your horoscope or as advised by your astrologer.

Quality: The translucent white dash resembling a Cat's eye is the Chatoyancy effect and holds great astrological value.

Metal: Silver is most suitable as per our knowledge and expertise.

Finger: The middle finger of the left hand for women and the right hand for men is our recommendation. 

Day: Tuesday.

Time: Morning during Krishna/Shukla Paksha.

Mantra: Om Ketvay Namah or Om Ketu Devtay Namah.

Upratna: Quartz cat eye, apatite cat’s eye.

Ketu can be quite the taskmaster. Hence, wearing a cat's eye can calm its malefic effects. It is known to overturn issues like health problems, conceiving a child, marital complications, and business losses. 
 
If Ketu favors you, then there is a meteoric rise in life and wealth. It makes you contemplate and analyze your past behavior and progress spiritually. There is a natural bent towards spirituality, awareness, acceptance, intricacy, and compassion.
 
An ill-placed Ketu results in peculiarity, hot-headedness, radicalism, and emotional problems. It sustains a gambling addiction and could also result in life-threatening diseases such as cancer. 
 
Its cosmic color is the invisible infrared, and it is seemingly in retrograde motion at all times. Wearing a Cat's Eye transforms these negative energies into positive outcomes. 

Wealth: It turns the dipping fortunes of the wearer by improving their financial stability. 

Health: It takes care of health-related issues and protects from negativity. 

Profession: It improves a declining business and prevents mishaps in professional matters. 

Spirituality: It improves your mental well-being and puts you on the path of contentment and spirituality. 

There are ten types of Cat's Eye available in the market. Of these, Chrysoberyl Cat's Eye, Quartz Cat's Eye, and Apatite Cat's eye are considered best for astrological purposes. The Chatoyancy effect, clarity, and caratage are top value determining factors for these gemstones. 
 
Colour - This stone comes in shades varying from grey, green to yellow with a white translucent dash across the surface. 
 
Clarity – The Chatoyancy effect is due to natural inclusions such as thin, parallel mineral fibers. The absence of spots and blemishes is a rare find. 
 
Caratage - A Cat's Eye with bright color and transparent clarity is challenging to find in higher caratage and hence precious. So, a two-carat gemstone would be one fourth the price of a four-carat in the same quality. Due to the easy availability of smaller sizes than the bigger ones, the more the carat weight, the higher the stone's cost.
 
Place of Origin - The Ceylon or Sri Lankan Cat's Eye is the most sought after, but those from Brazil, China, and India are equally suitable for astrological purposes. Chrysoberyl Cat's Eye is the most expensive of all Cat's Eyes. 
 
Treatment – Chrysoberyl Cat's eyes are best for astrological requirements. Generally, no treatments are done in a cat’s eye stone.
 
Certification - We are stringent with our quality standards and assure you of the best gemstones for your needs. Our Cat's Eyes come with a Private Lab Certificate. We can also provide a higher lab certificate like the GII or IGI at extra cost if required. Some of our gemstones are readily certified from both, GII (Gemological institute of India)  or IGI (International Gemological Institute)

Do note that the lab will certify all Cat's Eyes as 'Natural Cat's Eyes' only in the title. However, in the remarks or comments section, they will mention the variety. E.g., if the comments section cites ‘Chatoyancy effect’. 
Beware of similar looking glass made Cat’s eye sold in the market.