White Opal Pendant set in 925 sterling silver. The pendant head measure 26 mm in length ( opal size 16 mm x 8 mm ) stamped 925 Chain : 925 sterling silver / 40cm Opal is the national gemstone of Australia who produces more than 90% of the world's supply. White opals are found in South Australia in the major opal fields of Coober Pedy, Andamooka, and Mintabie. It has a white or milky base colour that is why it is called White Opal.  The exact colours of opal cannot be guaranteed.