Choosing Birthstones by Rashi - The Basics - Jothishi Budha or Mercury Rules Both Mithun (Gemini) and Kanya (Virgo) Budh influences the intellect and relationships. The ideal birthstone by Rashi for these lagnas is emerald. So, you should wear this gemstone on your little finger, or the Kanistha, on a Wednesday. Kataka Rashi or cancer sign is ruled by the Moon or Chandra