Muséum national d'histoire naturelle _ The species

FROM : Peyreblanque, Tarn, France
SIZE : 18.5 x 11.5 x 5.5 cm

This sample is a siderite. It shows lamellar crystals aggregates in rosette. They are opaque and have two shades: brown and black. Black crystals have this shade because they have changed at oxygen contact into indetermined manganese oxides.

This sample, acquired thanks to support from Total, comes from the french mines of Peyreblanque in Tarn. It is kept in the storage rooms of the collections (i.e., not yet displayed to the public).

Photography: A. Dahmane / Photo Saint-Hilaire, © MNHN.

SPECIE : Siderite

HISTORY : Name inspired by the Greek word "σιδεροσ" [sideros] meaning iron. Name given in reference to its chemical composition

Species first described in 1845 by Wilhelm Karl Ritter von Haidinger (1795-1871), Austrian geologist and mineralogist

Type-locality : undefined because species already known by the Ancients
ANCIENT NAME : Mine de fer spathique, fer carbonaté

CHEMICAL FORMULA : Fe CO3
CRYSTAL SYSTEM : Rhomboedric
COLOR : Yellow, brown, more scarcely gray or coulorless
DIAPHANIETY : Opaque to translucent
LUSTER : Vitreous to pearly
STREAK : White
MORPHOLOGY : Prismatic crystals, rhombohedra, scalenohedras, often massive
HARDNESS : 3,75-4,25
DENSITY : 3,932

CHEMICAL CLASS : V - Carbonates, nitrates
GROUP : Calcite
STRUNZ CLASS BEFORE 2001 : 5/B.02-40
STRUNZ CLASS AFTER 2001 : 5.AB.05

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Siderite

Siderite

MNHN N°207.41

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