The veins typically have chlorite, quartz and dolomite as gangue minerals. The gangue (the uneconomic waste material) is mainly quartz and pyrite or pyrrhotite. Natural iron ores are mixtures of iron and unwanted impurities, or "gangue". In this plant, zircon, rutile and ilmenite are separated from the silica gangue. Froth flotation uses hydrophobic and hydrophilic properties to separate the ore from the gangue. Gravity separation uses centrifugal forces and specific gravity of ores and gangue to separate them. The uranium is contained in autunite, uraninite, and coffinite, with gangue minerals pyrite and marcasite. Both have distinctive metal ratios and gangue minerals. Lithium is hard to separate from gangue due to similarities in the minerals. A residue containing gangue, barium, radium, and lead sulfates is left over. Secondly, the mineral is separated from the gangue. This makes the "marked" gangue particles float off with the graphite, yielding impure concentrate. The gangue that is found with lithium after the flotation are often iron bearing. The veins are composed of siderite, quartz and ankerite, with siderite making up the gangue. Gangue minerals include calcite, barite, and dolomite.