One Sea Opal, Opalite Cabochon. 

Sea Opal, Opalite 40x30mm size.  This is a created semi translucent milky white, with a hue of blue, sometimes some pink.  Domed top, flat back. Great paleness to bead around, make into a brooch. 

Picture is a representative sample of the actual bead. Some variances do occur.