The document provides 6 tips for buying cat's eye gemstones online: 1. Choose reputable online gem sellers with a good history and reviews. 2. Check the color of the stone, aiming for a light blue shade without dullness or excess shine. 3. Examine the hardness by checking for easy scratches, as cat's eye is very hard at 8.5 on the Mohs scale. 4. Be wary of marketing tactics like "sales" or "discounts", as synthetic stones may be sold at lower prices. 5. Ask for gemstone certification from the jeweler to verify properties and treatments. 6. Contact the provided numbers or websites for any additional queries.