What is pearl orient? To better understand, we must first take a quick look at how pearls are formed. When an irritant makes its way into the soft tissue of a mollusk, the mollusk secretes a composite material called nacre to smooth over the surface. Nacre is predominantly composed of aragonite (a calcium carbonate material) with traces of conchiolin (a protein). Left undisturbed, nacre will wrap layer by layer around the irritant and form, in time, the pearl.
These layers of nacre are like very thin plates stacked one upon the other. When these plates align, something quite brilliant happens: light reflected from the outer surface crashes into light reflected from the inner surface. This diffraction and interplay of white light produces the optical effect of iridescence. It is as if the pearl becomes a prism, separating light into the spectral colors of the rainbow. Traveling at different speeds and in different directions, some wavelengths dominate others – giving rise to dramatic flashes of color as the viewing angle shifts.
Typically, the thicker the nacre, the more spectacular this display of pearl orient. But not all pearls exhibit orient. Pearl color can be divided broadly into three characteristics. All pearls possess bodycolor, or the dominant, overall color of the pearl. Some pearls will have an overtone, or translucent color that appears over a large part of the pearl surface. Common overtones include pink, blue and green. Still less frequently, and indeed quite rarely, pearl orient will occur.
Pearl orient occurs when the layers of nacre are thick, well-formed and deep. Orient typically exhibits over a smaller area than overtone and is most often observed in natural pearls (which are composed entirely of nacre) and baroque or non-spherical pearls. These irregularly shaped pearls allow deeper layers of nacre to collect in ridges and grooves. Longer time within the mollusk enhances the potential for pearl orient, too. Round cultured pearls rarely exhibit pearl orient, but when they do the pearls are highly valued.
The nuanced, rainbow iridescence of pearl orient is important not solely for its aesthetic contribution to the pearl, but also for its indication of pearl quality and nacre thickness. The more perfect and lustrous the surface of the pearl, the higher chance it will have of displaying pearl orient.