Wearing Gemstones is sunnah Nabvi (PBUH)

It is Sunnah to wear the ring with the gemstone turned outward to the back of the hand (zhahir al-kaff) since that is how Ibn `Abbas said the Prophet (upon him blessings and peace) wore it, and how Ibn `Abbas himself wore it, – on the smallest finger of his right hand – as narrated by Abu Dawud and al-Tirmidhi in their Sunan, and the latter said al-Bukhari told him it was a “hasan sahih” hadith.