Luster is the measurement of the quality of light that is reflected by the pearls surface. The word luster (alternatively spelled lustre) is derived from the Latin word “lux,” meaning light.
Pearls are valued for seven factors, the most important of which is luster. Duller pearls have much less value than those with a high sheen, and many pearls with poor luster never make it onto the gem market at all.
A pearl’s luster is dependent on how each layer of the pearls nacre is developed, as well as the nacre’s translucence. Typically pearls with higher luster are those with a thicker nacre, which is the result of a longer development time within the oyster.
Pearls with excellent luster are so shiny that you can see objects reflected in them, while reflection in pearls with poor luster would be very dull or badly reflected. While all pearl types are capable of brilliant luster, Akoya pearls are prized for their inherent brightness and high shine.
PEARL OF WISDOM
There are many different types of luster across mineral categories. Even the term ‘pearly luster’ isn’t unique to pearls; it’s also used to describe the shine of minerals like muscovite and stilbite.