The　effects　of　siderite　on　reverse　flotation　of　hematite　were　investigated　using　micro　flotation,　adsorption　tests,　and　Fourier　transform　infrared　spectroscopy.　The　flotation　results　show　that　interactions　between　siderite　and　quartz　are　the　main　reasons　that　siderite　significantly　influences　the　floatability.　The　interactions　are　attributed　to　dissolved　siderite　species　and　fine　siderite　particles.　The　interaction　due　to　the　dissolved　species　is,　however,　dominant.　Derjaguin-Landau-Verwey-Overbeek　(DLVO)　theoretical　calculations　reveal　that　adhesion　on　quartz　increases　when　the　siderite　particle　size　decreases　and　that　fine　particles　partly　influence　quartz　floatability.　Chemical　solution　calculations　indicate　that　the　dissolved　species　of　siderite　might　convert　the　surface　of　active　quartz　to　CaCO3　precipitates　that　can　be　depressed　by　starch.　The　theoretical　calculations　are　in　good　agreement　with　the　results　of　adsorption　tests　and　FTIR　spectroscopy　and　explain　the　reasons　why　siderite　significantly　influences　reverse　flotation　of　hematite.