Abstract: The invention relates to a method for the preparation of transparent metal oxide pigment, in which a substantial portion of the silicon oxide is dissolved off from silicon dioxide based particles coated with transparent metal oxide, and to a transparent metal oxide pigment prepared by the method. In the extraction methods according to the prior art the problem is that in the extraction a part of the metal oxide is also dissolved, whereby thickness variations impairing the interference color of the metal oxide layer are created. Moreover, in the known methods hard-treated extraction chemicals which are detrimental for the environment are used. These problems have by means of the present invention been solved so that such particles are selected for the dissolution whose silicon dioxide portion is substantially soluble in base and metal oxide portion is substantially insoluble in base, and the dissolution is carried out by base.

Abstract: The invention relates to a new nacreous pigment which contains a dye or a color pigment and is based on metal-oxide-coated mica particles or other layer silicate particles, and to a method for preparing it. The pigment particles consist of metal-oxide-coated, porous silica skeletons of mica particles or of other silicate particles, containing few or no cations and having at least one dye or color pigment attached to them. In the method, a) a preliminary-stage product is prepared from mica particles or other layer silicate particles and a metal-oxide coating, the metal-oxide coating being poorly soluble or insoluble in acids, b) the thus obtained metal-oxide-coated mica particles or other layer particles are leached with a mineral acid, possibly together with an oxidant, and c) the dyeing of the thus produced metal-oxide-coated, porous silica skeletons of mica particles or of other layer silicate particles, containing few or no cations, is carried out using at least one dye or one color pigment.