@ harry_sandha,
Hessonite (Gomed), the gem for Rahu should be worn on the middle finger. The middle finger has been allocated to Shani (Saturn) and as vedic astrology states Rahu Vat Shani, Rhu can be worn on that finger.
Also, women should wear astrological gems on the left hand.
Wishing you good luck and may God bless you, and above all?
Cheers