Vintage sterling silver pendant set with a bright natural opal. This stone is small, but is is a fireball that actually sparkles like glitter in the sun. 

I believe that this is a repurposed stud post earring. There is a round plaque on the back that may have had a post. There is also old brown glue and Verdi gris in the solder where the bail was attached to the side of the setting. 

Stone measures 10mm by 10mm. Weight: 1.3 grams.