Emerald Opal Earrings Natural Gemstone Colombian Emerald & Ethiopian Welo Opal Earrings. 14K Yellow Gold Fill. May October Birthstone Gift - Natural Emerald gemstone! - not onyx, jade, glass or crystal. Stunning natural Colombian Emerald and firey genuine Ethiopian Welo Opal earrings measure 28mm (about 1-1/8 inch) in total length. Opals and emeralds measure approximately 7-8mm and 4-5mm in diameter respectively.