Muséum national d'histoire naturelle _ The species

FROM : Poonah, India
SIZE : 28 x 18 cm

It is microcrystals of prehnite coloured in light green-blue on which small white spheres of gyrolite crystals (zeolite uncommon) has developed. The stalactic shape of prehnite comes from an epimorphism (crystallization around a crystal pre-existent) of laumontite crystals. This sample measures 28 x 18 cm.

This specimen comes from Poonah area in India. The Muséum national d’Histoire naturelle could obtain it thanks to support from Total. It is kept in the storage rooms of the collections (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°190.97

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