Muséum national d'histoire naturelle _ The species

FROM : Lily mine, Pisco Umay, Ica departement, Peru
SIZE : 10 x 7.7 x 3.5 cm

This sample shows sheaves of centimetric and brilliant prismatic crystals on absolutely transparent gypsum crystals (detail 2). Some atacamite crystals are also developed within the gypsum crystals (detail 1).

This sample, acquired thanks to support from Total, was found at Lily mine, Pisco Umay, Ica departement, Peru. This mine has provided the best specimens of centimetric crystals of black green paratacamite associated to quartz (in contrast to atacamite that is associated to gypsum).

This sample is currently exposed in the Treasure Room, within the Gallery of Mineralogy of the Muséum national d’Histoire naturelle.

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

SPECIE : Atacamite

HISTORY : Named to recall its type-locality: the Atacama desert

Species described in 1801 by D. de Gallitzin. The species was already known and named since the end of the XVIIIth century from samples brought back from Peru by French explorer Dombey

Type-locality: Atacama desert, north of Chile
ANCIENT NAME : Cuivre muriaté, sable vert cuivreux du Pérou

CHEMICAL FORMULA : Cu2 Cl (OH)3
CRYSTAL SYSTEM : Orthorhombic
COLOR : Green to dark green
DIAPHANIETY : Transparent to translucent
LUSTER : Adamantine to vitreous
STREAK : Light green
MORPHOLOGY : Prismatic crystals, fibrous massive. Twins possible
HARDNESS : 3,0-3,5
DENSITY : 3,756

CHEMICAL CLASS : III - Halogenides
GROUP : Atacamite
STRUNZ CLASS BEFORE 2001 : 3/A.09-20
STRUNZ CLASS AFTER 2001 : 3.DA.10

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Atacamite

Atacamite

MNHN N°198.67

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