Pearls are sometimes heated in order to turn white-colored pearls into golden pearls, which are quite rare naturally.

Labs can detect heat-treated pearls through UV reflectance spectroscopy. Such pearls emit a brownish-orange color under UV lights, color concentrations in surface defects, and a greater concentration of color in the surface of the nacre.

Heat treatment is only applied to golden pearls. Apply the principle of "caveat emptor" when purchasing golden pearls. Real golden pearls are rare, so if the price seems too god to be true, it probably is.