Spherical shape, metallic pigment pigments

If you ever had the opportunity to use almninum pigments in plastics, you are familiar with the fact that you are not dealing with spherical pigments, but with flakes. Because of their shape, metallic pigments appear to behave in regard to their optical properties in almost every way opposite to non-metallic pigments. Here are some examples ... 

The stable form of arsenic is the gray or metallic form, although other forms are known. Cooling the vapor rapidly produces yellow arsenic, and an orthorhombic form is obtained if the vapor is condensed in the presence of mercury. Arsenic compounds are used in insecticides, herbicides, medicines, and pigments, and arsenic is used in alloys with copper and lead. A small amount of arsenic increases the surface tension of lead, which allows droplets of molten lead to assume a spherical shape, and this fact is utilized in the production of lead shot. 

Fine particles of malleable metals in elemental form are also used as pigments in coatings for aesthetic as well as protective purposes. They are generally platelet-shaped particles, but some are spherical. 

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