I've set a gorgeous 4mm Lightning Ridge opal on to one of the silver 'Tir' pendants.  The Opal is translucent, so is known as a crystla opal.  Lightning Ridge in Australia is where some of the World's most beautiful opals are mined. The pendant is supplied on a delicate 18"  trace chain.
 
Opal is the birthstone of October.  Opal is said to be good for clarity & positive manifestation.
 
Please email me if you have any queries.  I can always be reached at lydia@niziblian.com