A plateletlike two-phase pigment which has a core with a hematite structure of the composition where x is from 0.02 to 0.5, and an outer layer with a spinal structure of the composition where y is from 0.03 to 0.75 and z is from 0 to 0.5, can be prepared by a hydrothermal treatment of plateletlike Al.sub.x Fe.sub.2-x O.sub.3 pigments (x from 0.02 to 0.5) in the presence of a reducing agent dissolved in the aqueous phase.

The invention relates to a platelet-shaped pigment having high luster and high covering power or high transparency, consisting of a transparent, inorganic, platelet-shaped matrix which can contain an additional constituent, characterized in that the additional constituent is a soluble or insoluble colorant and in that the matrix is coated at least on one side with one or more thin, transparent or semi-transparent reflective layers of metal oxides or metals to achieve the luster.

Plateletlike pigments based on iron oxide and having a spinel structure of the composition: where u is from 0.01-0.09, v is from 0-0.3 and z is from 0-1. The pigments can be used for producing decorative coatings, in particular in paints, plastics, prints and cosmetics, for producing electromagnetic screens, as substrates for coatings and as pigments having magnetic properties.

A surface-treating agent for use in an inorganic pigment in which a metallic oxide layer and/or a hydrated metallic oxide layer is formed on the surface of said pigment, characterized in that said surface-treating agent contains one or more compounds selected from the group consisting of (1) a polyglycidyl ether compound, (2) a polyglycidyl ester compound, and (3) a diglycidyl polysiloxane compound.

Luster pigments useful for coloring paints, printing inks, plastics, glasses, ceramic products and decorative cosmetic preparations are based on multiply coated plateletlike metallic substrates comprising A) a first, colorless or selectively absorbing layer of metal oxide, B) a second, nonselectively absorbing layer of carbon, metal and/or metal oxide, and C) if desired a third, colorless or selectively absorbing layer of metal oxide.

Luster pigments based on multiply coated plateletlike silicatic substrates, obtainable by further coating substrates already coated with a first layer comprising a colorless or selectively absorbing metal oxide a) initially with a second, nonselectively absorbing layer consisting essentially of carbon, a metal or a metal oxide, and b) if desired subsequently with a third layer comprising colorless or selectively absorbing metal oxide, wherefor the carbon layer (step a) is applied by thermal deco...

Luster pigments useful for coloring paints, printing inks, plastics, glasses, ceramic products and decorative cosmetic preparations are based on multiply coated plateletlike metallic substrates comprising A) a first, colorless or selectively absorbing layer of metal oxide, B) a second, nonselectively absorbing layer of carbon, metal and/or metal oxide, and C) if desired a third, colorless or selectively absorbing layer of metal oxide.