The nine gemstones, or Navratnas, in Vedic astrology are associated with specific planets and are believed to offer various benefits when worn correctly. Here's a brief overview of each gemstone, its associated planet, benefits, and recommendations on when and who should wear them:

1. **Ruby (Sun)**: Represents power and authority, beneficial for those with a weak Sun in their horoscope, enhancing leadership and self-confidence. It should be worn on the ring finger on Sunday morning during Shukla Paksha 

2. **Pearl (Moon)**: Linked to emotional balance and stability, it's recommended for individuals facing anxieties or depression. Wear on the ring or little finger on Monday 

3. **Red Coral (Mars)**: Boosts energy, courage, and resolves Mars-related issues like Mangal Dosha. It should be worn on the ring finger on Tuesday

4. **Emerald (Mercury)**: Enhances communication skills, intelligence, and is particularly beneficial for businessmen. Wear on the little or ring finger on Wednesday

5. **Yellow Sapphire (Jupiter)**: Brings prosperity, wisdom, and marital happiness, especially beneficial for women. It's recommended to wear on the index finger on Thursday

6. **Diamond (Venus)**: Promotes love, beauty, and marital bliss, beneficial for enhancing career and health. Wear on the middle finger on Friday

7. **Blue Sapphire (Saturn)**: Offers protection, wealth, and good fortune but should be worn with caution as it can have strong effects. Wear on the middle finger on Saturday

8. **Hessonite (Rahu)**: Provides mental clarity and relief from the ill effects of Rahu. It's often worn to counteract confusion and enhance decision-making

9. **Cat's Eye (Ketu)**: Offers protection and liberation from the negative influences of Ketu, helping to overcome obstacles and fears.

The right gemstone, when worn properly, can bring balance, protection, and enhance positive aspects of your life as per Vedic astrology.