Annabergite Locality: Km-3 Mine, Lavrion Mines, Lavrion (Laurion; Laurium), Lavrion District Mines, Lavrion (Laurion; Laurium) District, Attikí (Attica; Attika) — Photo: Didier Descouens · CC BY-SA 3.0
Siderite
Also known as: Chalybite, Iron spar.
Iron carbonate — a tan-to-brown iron ore named from the Greek for iron, free of sulfur and phosphorus.
Intro adapted from Wikipedia (CC BY-SA).
Siderite is an IMA-recognized mineral species in the carbonate class, with the chemical formula Fe(CO₃).
It crystallizes in the hexagonal crystal system (space group R-3c). It is a member of the Calcite structural group.
Key properties: Mohs hardness 3.5–4.5; specific gravity 3.96; typically brown or yellow or gray or green; White streak; Vitreous, may be pearly or silky luster; refractive index 1.758; optically uniaxial.
IMA symbol Sd, IMA status: approved, named in 1845.
A common component of bedded sedimentary iron ores and metamorphic iron formations; in hydrothermal metallic veins; rarely in granite and nepheline syenite pegmatites; in carbonatites; authigenic, and in concretions.
It is found associated with Quartz, barite, fluorite, pyrite.
Its name comes from the Greek sideros, for iron in the composition.
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