muscovite: a colorless or pale brown mica with potassium
mica: any of various minerals consisting of hydrous silicates of aluminum or potassium etc. that crystallize in forms that allow perfect cleavage into very thin leaves; used as dielectrics because of their resistance to electricity
tyndall effect: the phenomenon in which light is scattered by very small particles in its path; it makes a beam of light visible; the scattered light is mainly blue