Rockwood Specialties Group, Inc.’s subsidiary, Rockwood Pigments (U.K.) Limited, has acquired the Pigments and Dispersions business of Johnson Matthey Plc for approximately $50 million.      The Pigments and Dispersions business produces transparent iron oxide pigments and dispersions, color concentrates and complex inorganic color pigments servicing the surface and wood coatings, plastics, building materials and printing ink markets. The business has 280 employees worldwide and annual sales ...