Editing Pearl (section)

===Gemological identification===
A well-equipped [[Gemology#Institutes, laboratories, schools, and publications|gem testing laboratory]] can distinguish natural pearls from cultured pearls by using gemological [[X-ray]] equipment to examine the center of a pearl. With X-rays, it is possible to see the growth rings of the pearl, where the layers of calcium carbonate are separated by thin layers of conchiolin. The differentiation of natural pearls from non-beaded cultured pearls can be very difficult without the use of this X-ray technique.

Natural and [[cultured pearl]]s can be distinguished from imitation pearls using a [[microscope]]. Another method of testing for imitations is to rub two pearls against each other. Imitation pearls are completely smooth, but natural and cultured pearls are composed of nacre platelets, making both feel slightly gritty.