What does "orient" refer to in relation to certain gemstones?

The term "orient" specifically refers to the phenomenon of iridescence that is observed in certain natural cultured pearls and mother-of-pearl. This optical effect occurs due to the layered structure of the nacre in pearls, which diffracts light and creates a play of colors that can shift depending on the angle of viewing and the light source. The beauty of this iridescent quality is a key characteristic that makes these gems highly valued.

In the context of gemstones, iridescence enriches the visual appeal and is a distinguishing feature when identifying natural cultured pearls. This aspect of "orient" is significant because it highlights the unique qualities that set certain gems apart from others, emphasizing the aesthetic experience they provide.