ColtanColtan (short for columbite–tantalites and known industrially as tantalite) is a dull black metalli...
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CassiteriteCassiterite is a tin oxide mineral, SnO2. It is generally opaque, but it is translucent in thin crystals....
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TungstenTungsten, or wolfram, is a chemical element with the symbol W and atomic number 74. The name tungsten com...
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