Vintage E Yazzie Southwestern Sterling Pendant Blue White Stones

Beautiful pendant composed of a marbled blue oval cabochon with an intriguing looking white mottled stone beneath. I think its a stone, but could be glass, I suppose. Great modernistic sleek Native American look and good size, at 1 3/4" x 5/8". Pendant is marked on back "E Yazzie Sterling". The chain is unmarked and doesnt look like its sterling silver --measures 24" long. Theres some light tarnish and a spot of light surface rust on the chain, otherwise no issues.