Take pearlescent pigments as an example, pearlescent pigments are a class of pigments with pearl luster, which are deposited on the substrate (generally natural mica, synthetic mica, glass sheet and other sheet-like materials) above a layer or alternately deposited multiple layers of metal oxides or non-metallic oxides and formed a flat sandwich body with a structure similar to sandwich. Due to the difference in refractive index between the substrate and the oxide deposited on its surface and each oxide, when the light shines on the surface of the pearlescent pigment, the incident light will be refracted and reflected at the interface of each layer of the pearlescent pigment, and the color of the pearlescent pigment that people see is the result of the superposition of light after multiple refractions and reflections of the light, that is, the interference phenomenon of light.

The common characteristics of mica group minerals are: layered silicate minerals, monoclinic crystal system, a few trigonal crystal system, the crystals are pseudo-hexagonal columnar, plate and sheet; The aggregate is scaly and foliaceous. It has a set of extremely complete cleavage, along which it is easy to peel into sheets. Therefore, the shape of mica is usually regarded as sheet.

X represents large interlayer cations, such as K+, Na+, Ca2+, Ba2+, Rb+, Cs+, etc. Y represents octahedral cations, such as Al3+, Fe2+, Mg2+, Cr3+, Ti4+, Fe3+, etc. Z is mainly Si4+ and Al3+; The ideal ratio of the additional anion (OH)- to (O)2- is 2:10, and (OH)- can be replaced by F- and Cl-. Most mica contain 4% to 5% water. Therefore, although they may be called mica, the chemical composition of different mica may be very different, for the purpose of research, we collectively refer to the minerals with this type of characteristics as mica group minerals.  

In addition, lepidolite and ferrolepidolite can also be used as mineral raw materials for extracting lithium.