Muséum national d'histoire naturelle _ The species

FROM : Wagholi, Maharashtra, Poonah, India
SIZE : 8.5 x 8.2 cm

This is crystallised pentagonite in a cavity. The whole specimen measures 8.5 x 8.2 cm. The crystals of pentagonite are not taller than 2 cm. They are intense blue and have a needle shape and brought together as gerbes.

This sample comes from the mineral deposit of Wagholi in Poonah area in India.

Acquired thanks to support from Total, it 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 : Pentagonite

HISTORY : Name inspired by the Greek word "πεντα" [penta] meaning "five", because of its tendancy to form aggregates of 5 crystals

Species first described in 1973 by Lloyd Staples, Howard Evans & James Lindsay

Type-locality: Lake Owyhee State Park, Malheur Co, Oregon, USA

CHEMICAL FORMULA : Ca (V+4 O) Si4O10 4H2O
CRYSTAL SYSTEM : Orthorhombic
COLOR : Blue, blue-green
DIAPHANIETY : Transparent
LUSTER : Vitreous
STREAK : Blueish white
MORPHOLOGY : Prismatic crystals, as spherical roses
HARDNESS : 3,0-4,0
DENSITY : 2,33

CHEMICAL CLASS : VIII - Silicates
GROUP : Cavansite-pentagonite
STRUNZ CLASS BEFORE 2001 : 8/H.36-20
STRUNZ CLASS AFTER 2001 : 9.EA.35

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Pentagonite

Pentagonite

MNHN N°202.339

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