That is pearl brilliance; the shine and glow of a pearl. The greater and deeper the luster is, the more valuable the pearl. Peals with a high luster display strong and sharp light reflections and a good contrast between the bright and darker areas of the pearl. Pearls with low luster look milky, chalky and dull. Select pearl jewelry that have a good luster.
The factors determining pearl quality also have an effect on the pearl grading factors originally.
What is Pearl Luster?
Pearl Luster is the factor that provides the pearl with its true beauty - it's that mysterious inner glow that seems to emanate from the center of a genuinely high-quality pearl. Usually, a pearl's luster is a combination of surface reflection and a glow that really does come from within - from the many layers of nacre built up over time inside an oyster.
Strong and sharp light reflections, and a good contrast between the bright and darker areas of the pearl will generally show pearls with a very high luster.
Here are some tips to judge Pearls Luster
Factor in determining a pearl's value. The more lustrous a pearl is, the more high quality. it's perceived to be and thus the more epensive it is. A truly lustrous pearl will have a jewel-like glow, with rainbow overtones. When a pearl appears too perfectly white or too dull and chalky, it is of low quality.
1. Look at the light reflections on the pearls. Usually, the less sharp and intense they are, the lower the luster. Sometimes, however, a lack of sharpness is due to surface blemishes, rather than the overall luster.
2. Under a light, there is a good contrast between the brightest and darkest areas of the pearls. The lower the contrast and the milkier the pearl are, the lower the luster. This is one of the quickest and easiest ways to spot low and very low luster. Milky-looking pearls are sometimes sold in "high quality" stores. Be aware that their luster is low.
3. Compare the luster of the individual pearls on the strand. They will almost always vary somewhat in luster. If possible, lay the pearls alongside other strands and compare the luster. This is most effective when you already know the relative quality of the comparison strands. Keep in mind that your impression of a strand will be affected by the pearls it is compared to. A strand will look better when viewed next to lower-luster strands than next to those of higher luster. The luster quality of a strand is determined by its overall appearance, not just by one pearl. Roll the pearls slightly so you can see their entire surface. The luster not only varies from pearl to pearl. It varies on the surface of each pearl.
Try the pearls on and check if you can see the highlighted spots on them from a distance (say 10 feet/3 meters). You'll be able to if the pearls are of good quality.
Other Pearl Quality Factors