This is an unusual handmade Japanese blue & white saltwater akoya cultured pearl burst brooch.

The pearls are 4.00-6.25mm round. They have great luster with pink overtones and colors ranging from dark blue/gray to cream and white. 

It is made of solid sterling silver and is quite large. It is a galaxy burst design from the 1950's-1960's. It measures 2 5/8 inches long. 

All pearls are truly vintage and have only been lightly cleaned.