siderite

{{Infobox mineral | name = Siderite | category = Carbonate mineral | boxwidth = | boxbgcolor = | image = Harvard Museum of Natural History. Siderite. Gilman, Eagle Co., CO (DerHexer) 2012-07-20.jpg | imagesize = 260px | alt = | caption = | formula = FeCO3 | IMAsymbol = Sd | strunz = 5.AB.05 | dana = 14.01.01.03 | system = Trigonal | class = Hexagonal scalenohedral (m) H-M symbol: ( 2/m) | symmetry = Rc | unit cell = a = 4.6916 c = 15.3796 [Å]; Z = 6 | color = Pale yellow to tan, grey, brown, green, red, black and sometimes nearly colorless | habit = Tabular crystals, often curved; botryoidal to massive | twinning = Lamellar uncommon on{012} | cleavage = Perfect on {011} | fracture = Uneven to conchoidal | tenacity = Brittle | mohs = 3.75–4.25 | luster = Vitreous, may be silky to pearly | streak = White | diaphaneity = Translucent to subtranslucent | gravity = 3.96 | density = | polish = | opticalprop = Uniaxial (−) | refractive = nω = 1.875 nε = 1.633 | birefringence = δ = 0.242 | pleochroism = | 2V = | dispersion = Strong | extinction = | length fast/slow = | fluorescence= | absorption = | melt = | fusibility = | diagnostic = | solubility = | other = | alteration = | references = }}

Siderite is a mineral composed of iron(II) carbonate (FeCO3). Its name comes from the Ancient Greek word (), meaning "iron". A valuable iron ore, it consists of 48% iron and lacks sulfur and phosphorus. Zinc, magnesium, and manganese commonly substitute for the iron, resulting in the siderite-smithsonite, siderite-magnesite, and siderite-rhodochrosite solid solution series.