Wolframite. Close-up of a section through wolframite ((Fe,Mn)WO4), the principle ore for the metal tungsten (W). Wolframite forms tubular crystals. Tungsten is used in electric lamp and heating elements, in industrial alloys, and in electric contacts. The spectral colours (top) are from a thin layer of chalcopyrite (copper pyrites, CuFeS2), which is an important ore of copper.
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