Transmission electron microscopy (TEM) and STEM reveal the exsolution lamellar structure in labradorite, which is responsible for the iridescence of labradorite. The labradorite is made up of calc-poor and calc-rich plagioclase, and its thickness is mainly controlled by calc-rich plagioclase. The more the cal c content, the thicker the lamellar, and the longer the wavelength of the interf erence color. Furthermore, the increasing speed of calc-rich plagioclase will surpass that of the calc-poor one. The selected area electron diffraction (SAED) shows that the direction of exsolution lamellar structure is (153) , which is nearly parallel to （010）. The uniform interference color may have different calc con tents and exsolution directions, varying from place to place and from environment to environment.