This is a single earring, described originally to have looked like "a silver bit of net with a blue stone caught in it". It has a pin and and a sort of clasp that holds it in place.
Initially a gift from Burrich to his 'master' Chivalry, this earring was a family heirloom that Burrich inherited from his grandmother. She was probably a freed slave laterly of the Butran Clan and it was most likely her Freeman's Earring. Upon Chivalry's death his wife Patience inherited the earring and, probably not realising its significance, gifted it to the young Fitz before his trip to the Mountain Kingdom.
It holds great significance to Burrich, possibly representing a master/servant bond between him and who so ever wears it. It is of fine workmanship, taking the form of a small sapphire entrapped in a finely linked silver mesh.
A collector in Landing offered to buy it for 3 gold pieces.
Amber wears a very similar earring.
When Lord Golden re-appears in Fitz's life he offers to return the earring to him, as he had not passed it on as requested. Fitz tells him to keep it, and so in order to wear in un-noticed at court Golden crafts a new earring around it, in the shape of a silver globe.
Lord Golden later returns the earring back to Fitz who in turn then passes it on to Swift.