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an intermediate product or a by-product in nonferrous metallurgy. A matte is an alloy of variable chemical composition that consists of iron sulfide and sulfides of nonferrous metals.
Owing to the low solubility of sulfides of nonferrous metals in oxide melts, the relatively low melting point (below 1100°C) of such sulfides, and the high density (greater than 4 g/cm3) of the sulfides, a molten matte separates from a slag upon smelting and forms a separate layer below the slag. A matte is a primary product into which copper, nickel, and cobalt go when a copper sulfide or nickel sulfide raw material is smelted or when oxide ores are processed by means of certain techniques. Mattes usually contain 10–50 percent Cu and Ni, 15–25 percent S, and Fe as the remainder.. Mattes are also produced in lead smelting when copper and sulfur are present in the raw material. As a rule, noble metals and metal impurities in raw materials accumulate in mattes.
Mattes are processed in a converter (seeCONVERTER BLOWING OF MATTE), where the sulfur is oxidized and the iron is converted from the sulfide form to the oxide form and, together with silica, yields converter slag. The copper sulfide and nickel sulfide are subjected to further processing after the iron is removed.
Nickel matte produced in smelting is sometimes called raw matte. A matte that is produced after converter blowing and has an iron content of less than 3 percent is referred to as converter matte. A matte with an intermediate iron content is known as furnace matte. Copper matte that is produced after the completion of the first blowing period and contains < 1 percent Fe is called white matte.
I. D. REZNIK