| Hi Richard,
Overtone is a secondary color impression and can be enhanced by dying (in that case I call that undertone like the blush effect on akoyas) or vapor deposition. Natural overtone in collector world is called "color spill" and refers to the effect of a pearl having a colored fringe around its shadow when put on a white surface in direct light.
Orient is a prismatic effect and, in contrast to overtone, moves. Although the so-called wild-water orient looks like it is only on the surface as in niobium treated pearls, the real thing in natural and solid-nacre cultured pearls or such with very-thick-nacre can be observed by candling. Just hold the pearls up to an intense white light source and you will observe the rainbow colors inside the pearl through transmitted light. This test also works with dark pearls. Dark pearls with natural orient have to have highly transparent, albeit dark, nacre to create this effect. If you cannot verify the transparency by candling with a 100W clear light bulb, any orient-like effect the pearl exhibits is questionable in its origin.
Zeide  |