Abstract: The invention relates to a process for jet grinding inorganic pigments comprising the steps of compacting the inorganic pigments on a roller compactor at a predetermined linear force, and jet grinding the compacted inorganic pigments.

Abstract: A process for preparing red ceramic molded bodies by rapid firing is disclosed, wherein low Si-content iron oxides are employed. The process produces molded bodies having improved colouristic properties.

Abstract: A temperature-resistant black pigment which is a mixed oxide of manganese and iron with the structure of hematite and having a manganese content of 3 to 35% by weight, and with absolute color values in colorimetric testing in paint systems, expressed in CIELAB units, in the lightened form (Blend of 10 parts titaniumdioxide and 1 part of black pigment) of 60 to 70 for L*, -0.5 to 1.9 for a* and -4 to -6.5 for b* useful for coloring autoclave-cured building materials and for pigmenting heat-resistant paint systems is obtained by preparing a precursor material of manganese and iron oxides or hydroxides, which contains the phase with the structure of spinel and calcining that precursor material in an oxidizing atmosphere at 500.degree. to 1,000.degree. C.

Abstract: Spinel black pigments are prepared by annealing oxides, hydroxides or carbonates of copper, chromium and manganese and grinding the product. The manganese-yielding component is Mn.sub.3 O.sub.4.

Abstract: A black manganese/iron oxide pigment having a spinel structure and having the composition Mn.sub.x Fe.sub.3-x O.sub.4 wherein x has a value from 0.1 to 0.9, is prepared by the steps:a) oxidizing iron(II) salts or mixtures of iron(II) salts and manganese(II) salts, in solution or after reaction with alkaline precipitants, with manganese dioxide or other compounds containing manganese in high valency,b) additionally oxidizing the salts of (a) to establish an Fe(III) content therein with another oxidizing agent, andc) filtering, washing, drying and grinding the pigment;and the pigment is useful for pigmenting building materials to a black color.

Abstract: A black manganese/iron oxide pigment having a spinel structure and having the composition Mn.sub.x Fe.sub.3-x O.sub.4 wherein x has a value from 0.1 to 0.9, is prepared by the steps:a) oxidizing iron(II) salts or mixtures of iron(II) salts and manganese(II) salts, in solution or after reaction with alkaline precipitants, with manganese dioxide or other compounds containing manganese in high valency,b) additionally oxidizing the salts of (a) to establish an Fe(III) content therein with another oxidizing agent, andc) filtering, washing, drying and grinding the pigment;and the pigment is useful for pigmenting building materials to a black color.

Abstract: Pigments having the color of natural uncalcined umber contain more than 85% by weight of iron oxides, expressed as Fe.sub.2 O.sub.3, and less than 0.1% by weight of crystalline silica are obtained by mixing iron oxides of spinel structure and/or hematite structure with or without iron oxide yellow and said pigments are useful in coloring paints, lacquers and building materials.