Mica is well-known for its ready delamination, even in the form of large sheets. This is due to the relatively weak bonding effect of the univalent counterion. Figure 2 is a photomicrograph of muscovite plates.
White nacreous pigments are made by forming a uniform coating of TiO2 on delaminated mica. The mica serves as a transparent template so that the high refractive index TiO2 can assume the required platy shape. Pearlescence is optimized when the pigment’s optical thickness (platelet thickness times refractive index) is in the 100nm (blue white) to 140nm (yellow white) range. Thicker platelets are used to make interference colors. Light interference is created by interaction of the reflections from the upper and lower surfaces of the platelet. A reflection maximum occurs at the wavelength of light for which these two reflections are in phase. A reflection minimum occurs at the wavelength for which they are exactly out of phase, canceling each other out. A transparent, colorless nacreous pigment platelet acts as a filter, separating light into two components: the reflected color and the complementary transmission color.