Evaluating Pearls - Lustre and Orient

What creates instant eye appeal in a good pearl is its alluring lustre - the intense brightness created as light travels through the many layers of nacre and is reflected back to the viewer's eye from deep within the pearl. Lustre is evaluated on the degree of brightness observed, which in turn is influenced by the thickness of the nacre. Orient is the iridescent, shimmering play-of-colour that occurs when the nacre is particularly thick and well-formed. This visually appealing characteristic, readily seen when the pearl is rotated, generally adds value to the pearl.