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.
|categories of lustre|
|excellent||Exceptional degree of surface reflectivity and shine. The reflection of a nearby object in bright, diffused lighting is mirror-like and well defined.|
|high||Lesser degree of surface reflectivity and shine than 'Excellent' but producing a very clear reflection. The reflection of a nearby object in bright, diffused lighting is well defined and clear.|
|average||Degree of surface reflectivity and shine is of average appearance. The reflection of a nearby object in bright, diffused lighting may range from good to slightly dull.|
|dull||Surface reflectivity and shine appears chalky, milky or dull. There is very little reflection of a nearby object in bright, diffused lighting.|