Muséum national d'histoire naturelle _ The species

FROM : Malosa Mountains, Zomba Plateau, Malawi
SIZE : 9.8 x 5.8 x 5 cm

This sample presents arfvedsonite crystals on a matrix made of ecru crystals of microcline. The arfvedsonite is here striated tabular crystals, black and opaque. The whole specimen measures 9.8 x 5.8 x 5 cm.

It comes from Malosa Mountain in Malawi. Acquired thanks to support from Total, it is kept today in the storage rooms of the collections (i.e., not yet displayed to the public) of the Muséum national d’Histoire naturelle.

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

SPECIE : Arfvedsonite

HISTORY : Species dedicated to Johan A. Arfvedson (1792-1841), Swedish chemist

Species described in 1823 by Henry James Brooke (1771–1857), English mineralogist

Type-locality: Compexe de Ilimaussaq, Province de Kitaa, Groënland
ANCIENT NAME : Horneblende ferrifère

CHEMICAL FORMULA : Na 3 [(Fe 2+;Mg) 4 Fe 3+] Si 8O 22 (OH) 2
CRYSTAL SYSTEM : Monoclinic
COLOR : Dark green to blueish black
DIAPHANIETY : Transparent to opaque
LUSTER : Vitreous
STREAK : Bright gray to gray black
MORPHOLOGY : Elongated crystals, striated. Fibrous radial aggregates
HARDNESS : 5,0-6,0
DENSITY : 3,33

CHEMICAL CLASS : VIII - Silicates
GROUP : Amphibole
STRUNZ CLASS BEFORE 2001 : 8/F.08-100
STRUNZ CLASS AFTER 2001 : 9.DE.25

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Arfvedsonite

Arfvedsonite

MNHN N°206.79

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