Muséum national d'histoire naturelle _ The species

FROM : Brandberg, Namibia
SIZE : 6.8 x 6.5 cm. Sphere 2.8 cm

This sphere of aqua-green crystals of prehnite measures 2.8 cm in diameter and the whole sample measures 6.8 x 6.5 cm. The sphere is on a matrix of white quartz microcrystals.

This sample, acquired thanks to support from Total, comes from Brandberg in Namibia. It is kept in the storage rooms of the collections of the Muséum national d'Histoire naturelle (i.e., not yet displayed to the public).

Photography: Louis-Dominique Bayle, © MNHN.

SPECIE : Prehnite

HISTORY : Species dedicated to the Dutch colonel Hendrik von Prehn (1733-1785) who discovered the mineral

Species first described in 1788 by Abraham Gottlob Werner (1749-1817), German geologist, Bergwerk Akademie, Freiberg, Germany

Type-locality: The Cap, Republic of South Africa

CHEMICAL FORMULA : Ca2 Al2 Si3 O10 (OH)2
CRYSTAL SYSTEM : Orthorhombic
COLOR : Yellow, gray, green pale, dark green, green, pink
DIAPHANIETY : Semi-transparent to translucent
LUSTER : Vitreous to pearly
STREAK : White
MORPHOLOGY : Crystals are rare, spherical aggregates, compact
HARDNESS : 6,0-6,5
DENSITY : 2,90

CHEMICAL CLASS : VIII - Silicates
GROUP : Prehnite
STRUNZ CLASS BEFORE 2001 : 8/G.07-30
STRUNZ CLASS AFTER 2001 : 9.DP.20

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Prehnite

Prehnite

MNHN N°193.38

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